NOTE: This spoiler sent in by Brentage5000.

The movie starts out with a guy named Roger (Jon Heder) waking up for his job as a meter maid in New York City. In his apartment we see tons of self help books...and I mean that in the weight sense. On the streets, he starts writing a parking ticket when two big black guys come up. They explain that they were just about to move the car, and Roger says okay, and things seem fine until he explains that the ticket has already been processed. They get mad at him and he jumps in his little car, but they outwalk him. He takes off down a hill and one of them pulls out a gun and shoots the car. Roger collapses, and the two guys freak out. Roger wakes up and we realize he fainted as he explains that he has anxiety attacks. To show the guy who "shot" him there's no hard feelings he gives him eighty bucks to pay the ticket. The guy's friend, on the other hand, says he needs some compensation for all the mental anguish he just went through...

Later, we see Roger -- sans uniform -- in the office of his supervisor, Sergeant Moorhead (Luis Guzman). He's getting chewed out and requests time with his life counselor, which his contract says he gets. Moorhead switches hats and -- surprise! -- becomes Roger's life counselor. Anyway, Roger eventually gets home and has the next day off. As he heads out to his job of big brothering, he sees his cute Australian neighbor Amanda (Jacinda Barret) and her roommate Becky (Sarah Silverman) heading to the gym for tennis practice. Since Roger has a huge crush on Amanda, he tries to ask her out, but fails and gets mocked by sarcastic-abusive Becky. Depressed, he goes out onto the street but at the YMCA type building is told by head guy Ian (David Cross) that Mike (the kid) wanted a different big brother, and since this is the third time Ian thinks Roger should try somewhere else or take a break. Roger breaks down crying and as an effort to console him, Ian gives him the number of a confidence building guy, and he tells him two things -- don't say where he got the number, and burn it if he doesn't use it.

That night, we see Roger debating over whether or not to dial the number on the paper. Ultimately he does, and a voice says wearily, "Hello." Roger starts talking but then the voice cuts in, "If you are calling about the class, press one now." Roger asks if this is a recording, and the voice says, "Just press one, dipshit." Roger hangs up but is star-sixty-nined and the guy proclaims him his worst student yet just before telling him to bring five thousand dollars in a plain manilla envelope to the fourth floor of the rec center tomorrow night. Roger does this and the next night he and another guy both arrive and are stopped in an elevator by a big black guy named Lesher (Michael Clarke Duncan -- ROCK!!!) who seems to be an enforcer for this guy. He takes the money and after telling them there will be no talking unless they are spoken to and chastising Roger for bringing his money in a plain white envelope, the elevator resumes. Inside the classroom, every desk but one is full and Roger and the other guy, Walsh (Matt Walsh), argue over who doesn't get it. The guy behind the desk gets fed up and yells at one of them to take it and Walsh squeezes in there. The other guy gets up and reveals himself as Dr. P (Billy Bob Thornton), the one who brought them all here. He verbally abuses them for a little bit -- especially some poor sap named Diego (Horatio Sanz) whose wife beats him -- takes the money, lets them know what they're in for, and walks out.

The next day, we see Roger sneaking out of his bedroom in his pajamas in the morning to dump some trash. As he's in the closet with the chute, he hears Amanda coming and hides, but she opens up the closet and finds him. The two share a brief moment, but then Amanda has to leave for her job at a bookstore. That night, the class is watching some documentary on lions and Dr. P. is talking about why they're so great -- he claims that their secret is their roar, which automatically lets other animals know that they're tough and mean business, and pretty soon the whole class is chanting, "WE ARE LIONS! WE ARE LIONS!" As Dr. P. leaves, we see Lesher giving out little beepers to everyone. He tells the class that whenever the beepers go off they have to initiate a confrontation with anyone nearby, and if they don't they will be expelled from the course. A couple of the guys laugh, and one bald guy, Eli (Todd Louiso), jokingly asks if this means they're all going to be under heavy surveillance. Lesher cracks up at this and then mutters in a deadly deadpan, "Yes."

A couple of days later, we see Roger in the breakroom at work where he is being picked on -- though not directly -- by the village loudmouth. Just then his beeper goes off, paving the way for more taunts. Roger mulls things over and as the loudmouth gets up with his prize Star magazine and opens the vending machine for the last bear claw, Roger dives in and grabs them both, savoring everything. He and the loudmouth start shoving each other and....Roger gets a swirlie (ask your kids). This sets off a montage of all the students initiating confrontations only to be beat up by their "targets". We then see all the students in the forest where Dr. P. is mocking some letters they wrote about their goals for the class (especially Walsh, who wrote "I want to move out of my parents' basement). He then tells them that the reason for them being here is because he has set up a paintball tournament that starts -- BIFF! -- immediately. They all grab guns and scramble, but slowly they start getting picked off by Lansher, who is in full-on commando mode. Soon there's just Roger, Walsh, Eli, and Diego still left, and Lansher gets the drop on all but Roger and has them take their clothes off and bend over. Later, Roger comes sliding down a ridge and sees the three bent over and crying while Lansher strolls back and forth taunting them and looking like the cat who caught a canary, then lost it and followed it to a whole houseful of canarys. Roger sneaks up behind him, grabs his giant crossbow gun...and manages to shoot him right in the head, taking him down for the count.

That night at a bar, we see everyone partying and singing karaoke, and everyone is real proud of Roger's takedown of Lansher. Dr. P. calls Roger over and congratulates him and asks why he took the course and finds out it was because of Amanda. He asks Roger a few questions about her and then tells Roger he doesn't need the course...he should just go and ask her. The next day, Roger is doing just that, but as soon as Becky opens the door, he starts panicking and when Amanda enters after hanging up the phone from her parents (in Australia, natch), he faints entirely. He soon wakes up inside the apartment and as he's excusing himself actually manages to ask Amanda out (he wasn't looking at her so that might have had something to do with it). The next scene is Eli out on a date with some blonde girl who we soon find out is Lansher in disguise, and Dr. P. goes over the six rules of dating--

1 - Be dangerous; it's cool
2 - No compliments, EVER!!!
3 - Always get the girl alone
4 - Wherever you are, the place is lame!
5 - Relate to her
6 - Lie, lie, and lie some more

Roger raises his hand at this point and asks what to do if you want a real girlfriend, and Dr. P. just looks at him and says, "Let's work on getting you laid first, alright?"

That night we see Amanda and Roger at a fairly fancy restaurant where she talks all about herself and he tries to do everything Dr. P. said (he even has flash cards with him). At one point she comments on the meal choice of a nearby guy who ordered a lobster by saying if you listen closely while boiling the lobster, you can hear it scream. This inspires Roger to grab a bag, stick all the lobsters in it, take Amanda, and run like hell for the docks, which they actually pull off. They almost kiss when all the beer Roger has drunk catches up with him and, since he's never been drunk before, he doesn't know which way is left. Amanda gets him back in his bed and he says, "Amanda....I totally love you," but she just chalks it up to alcohol and kisses him good night.

The next day, Roger is feeling pretty good about himself when he sees the toughs who took his uniform earlier playing basketball....IN HIS SNEAKERS!!! He wanders onto the court, deflates the ball, and demands his uniform back. The inevitable beatdown is interrupted by the guys' mother, who disciplines and embarrasses them into giving the sneakers back. Later, while Roger is talking with his friend Ian, who cautions him not to stand out too much, we see Dr. P making time with Amanda, who thinks he's a spinal surgeon/widower named Dennis. Ian tells Roger that there was a guy named Lonnie Finestein who took the class and was doing really well, and P just tore his life apart out of jealousy or something. Worried, Roger gets some flowers and heads to Amanda's apartment, only to find Becky. He gives the flowers to her instead and asks where Amanda is (her idea). We next see him walking on the street in the rain when he sees P and Amanda in some cafe together. Later, we see P go into an empty classroom where Roger is waiting for him. Roger asks what's going on and P tells him it's a competition to test Roger, and may the best lion win.

A couple of days later we see P and the girls at a tennis stadium when Roger comes up and goes to Amanda (who's next to P), "Oh, hi Amanda! Is this your dad?" The two get "introduced" and they decide to play girls against boys. As the girls walk away, P compliments Roger on the Dad comment and gets told that there's more coming. By the end of the match, Roger has accidentally hit Dennis with at least four serves and the two get down on the floor. Roger leaves, but not before hitting that automatic ball server hard enough to make one ball--

Later on, we see Roger explaining his situation to Eli, Diego, and Walsh, who he's gotten pretty close with. The three say he's being ridiculous and la-de-da "Dr. P. is a golden god". Walsh says that if they tried anything, Lesher would probably try to rape them or something, and the other two look alarmed at this as Roger goes, "What?" He leaves, and Diego and Eli go, "You swore you'd never talk about that," which explains what Lansher did to them that day. Meanwhile, at Amanda's apartment, we see that it has been covered with stalkeritti (stalker graffiti) supposedly from Roger and two police (actually more guys from the group) are checking it out, including the spray painted dog. As Amanda and Becky go to the dog, P gets up from his spot on the couch and goes to one of the guys, "You spray painted the dog?" At this point Roger comes in and the "cops" start trying to arrest him, and after a few minutes and a fall through a glass table, they succeed. They take him away and in the elevator jokingly spray him with some pepper spray, but the one who does it used too much and filled up the whole elevator with it, blinding all three of them.

A few nights later, we see Lesher and P coming out of a museum only to find their car being towed. Roger pops out from behind the ccar and says that according to his chalk, the car was three inches into the fire hydrant zone, making it eligible for towing. He gives them their ticket and walks off smiling. He's not smiling as much the next day, though, when his boss is reading a love letter that Roger supposedly wrote him. Roger tries to explain, but the boss says that although it's the most beautiful thing anyone has ever said to him, he can't have Roger work here any longer. Not long after this, Roger and P meet in a museum at night. P says, "You know...I like it here. It's real quiet....helps me think, you know?" and then offers a truce -- they leave each other alone, and P gives back half of Roger's tuition payment (since he did learn something). He then tells Roger that he and Amanda are headed for Miami that Friday (for a medical conference), and that Roger should just avoid Amanda from now on.

The next day, we see Roger heading north on a train. He comes to a house and rings the doorbell asking for Lonnie. Lo and beheld, the infamous Lonnie Finestein (Ben Stiller) opens the door. After convincing Lonnie that he wasn't sent by P, Lonnie lets him in and tells his story -- he used to be a Vietnam soldier but got pissed on by the country. He took P's class to get himself back and did okay -- got a new girlfriend and a new place to live, cleaned himself up, etc. After three months, though, P came along again and stole it all away from him. He then shows Roger a scrapbook he's collected of P, and it turns out he's a former real estate guy who got into some trouble. There's even some pictures of him and his wife together in there. Roger tells Lonnie that the same thing is happening to him and he wants to use Lonnie's help to stop P and Lansher. Lonnie freezes at the mention of Lansher and then agrees.

Back in the city, Roger shows Diego, Walsh, and Eli everything Lonnie had, but they still aren't going for it. Eli explains that he's dating a girl who thinks he's Moby, and the others think they look too cool to do this, but they eventually come around on one condition -- they don't deal with Lansher. Roger agrees, and the next day we see Diego and Eli at an airport pretending to be Homeland Security agents in need of the passenger manifest for P's flight to Miami. They get the list (astonishing, I know) and confirm that P and Amanda are both on it. Saturday rolls around, and we see Eli on radio connecting everyone. Meanwhile, we see Lansher in a chauffeurs uniform in front of Amanda's building picking her up to take her to the airport. He tells her to take her time coming down and goes back to the town car he rented for the occasion (better than the clunker he was driving). As soon as he gets in, Lonnie pops up from the backseat and grins. Lansher barely has time to go, "Oh, shit--" before being chloroformed. Lonnie crawls into the front seat and pulls away just as Diego pulls up with his own town car and chauffer's outfit. He greets Amanda and throws her bags in the trunk and they're off. He radios Eli that they're good and Eli calls first Walsh, who confirms that P's wife is still at home, and then Lonnie, who says that this is where he gets off, since he and Lansher have some unfinished business. He throws his radio out the window and we see Lansher in the back seat, stripped to his underwear, bound with duct tape, and looking scared to death.

At the airport, we see P calmly waiting for Amanda. We then cut to Amanda and Diego, who are actually headed for P's wife. Back at the airport, Roger marches up to P and confronts him with everything he's learned, and P....applauds. He tells Roger that he does this every year with the best student in the class, and Roger is just the first guy to actually do everything he needed. Roger realizes that this means Lonnie chose withdrawal instead of going all the way and is really just a kook (Well, DUH!). P then pulls out two plane tickets and shows him whose names are on them -- Roger's and Amanda's. Realizing what he's done, Roger grabs his walkie-talkie and tells Eli to abort. Eli gets on the horn to Diego, who whips the wheel around and barely makes it back to JFK. Amanda gets checked in, rides the escalator to the top, and there waiting for her is....Dr. P. Meanwhile, we see Roger waiting at the top of another escalator without Amanda on it, and he realizes that P pulled one over on him again. He calls Eli and asks what terminal the plane is in and when he hears Terminal 4 and sees that he's in Terminal 8 he runs like hell, slowing only to go through the metal detector, where he leaves his shoes behind despite the calls of the people running it. He makes it onto the plane and tries to confront P but starts having a panic attack. He collapses and a stewardess goes for a first aid kit, but Amanda says it's alright -- after all, Dennis is a doctor. Not having a choice, P plays along. He bends over Roger and listens for breath, but instead hears, "It's your move....DOCTOR." He shouts for the paddles and prepares to zap him at full voltage (1800 volts, that is) when someone says that the thing isn't even charged. P recovers and blames the stewardess for not turning it on, since he thought she had. The stewardess looks humbled and P gives Roger one last chance, but Roger stays still. P readies to shock him when Amanda notices that Roger is breathing. P starts yelling at her to shut up and let him work, and she realizes that Roger was telling the truth all along, and he admits it....except for the part about spray painting her dog, which he didn't do. Roger sits up and starts talking, but he accidentally knocks the paddles into P's crotch and sets them off, sending 1800 currents through P's balls...although when P drops the paddles, they end up landing on Roger's stomach, sending some of it there too. Just before Roger passes out from the pain, he says again, "Amanda....I totally love you." She smiles and this time kisses him.

Some time later, we see P at the museum again, in front of a display of lions. Roger comes up behind him and says, "You know...I like it here. It's real quiet....helps me think, you know?" The two talk, and we find out that P's wife found out about everything and kicked him out of the house. Even worse, she found out how his real estate money had really been coming from the class. Roger, on the other hand, says how things are going great for him and Amanda and they're heading to Miami at the end of the month. P grimaces and then gives Roger something he never gave to any of his students before -- a diploma. The two recognize each other as equals and go their separate ways.

As the credits start, we see little epilogues:

Lonnie and Lansher were never heard from again, but we see them in a jungle in southeast Asia where Lonnie promises to give Lansher an eight-minute head start.

Walsh eventually moved out of his parents basement and got an apartment in the city...with his grandparents.

Diego left his wife and started dating Becky, and is apparently much happier now, despite her constant verbal abuse of him.

Eli got married to that girl he was dating, and she still thinks he's Moby.

As for Roger and Amanda, they took their trip to Miami where Roger finally had sex for the first time.