NOTE: This spoiler was sent in by Robert Workman at GameDaily.com who says..."The movie wasn't half bad. It didn't do a total riff on Madagascar and had some good moments. Not the best Disney caliber, but it's fun."
The movie begins with Samson (voiced by Kiefer Sutherland) speaking to his son Ryan about his old adventure days in "the wild", where he fought off a number of wildebeests with a mere roar. Ryan learns that his roar isn't really that mighty, and instead makes the visitors at their exhibit at the New York Zoo laugh at him. Samson backs his with his own roar to keep them in line. The zoo soon shuts down, and the animals make their way out of the exhibits to head to an event that's like curling, but uses turtles instead of discs.
It's here we're introduced to a number of Samson's friends- Benny the Squirrel (James Belushi), Nigel the Koala (Eddie Izzard), Bridget the Giraffe (Jeannine Garafalo) and Larry, a dim-witted Snake (Richard Kind). Oddly enough, Benny has a thing for Bridget, although it's not the other way around. They all work together on one of the curling teams, and Samson invites Ryan to come along. Depressed he does not have a mighty roar, Ryan says he'll catch up to Samson later. Meanwhile, after he leaves, a troublesome rhino and kangaroo, two of Ryan's friends, show up and ask him to come along to scare some herding gazelles.
The curling competition begins, and the penguin team the animals are facing are doing extremely well. Nigel finds himself distracted by fans who are carrying around stuffed koala dolls with bad speech, and is soon picked up by them. The team calls upon a "trick play" to get a turtle on the bullseye, and it gets disastrous, with Larry wrapping around Bridget and sliding along. Miraculously, the turtle ends up on the bullseye, but soon a stampede breaks out when Ryan inadvertently causes the gazelle to run wild. The animals survive, but Ryan is exposed, and Samson chews him out for costing them the game. He tries to apologize, but Ryan runs off, hiding out in a "green box" in hopes of getting away from the zoo- something Samson told him to avoid.
Early morning comes, and the "green box" is loaded up to be taken away, with Ryan still inside- although he now has second thoughts about leaving. Samson spots him just as the "box" is taken away, and he and his friends soon summon some pigeons to track him down. It turns out that the "green boxes" are taken to a port by the Statue of Liberty, and Samson sets out on a rescue mission to save Ryan, hiding out in a garbage bin and picked up by a truck. His friends tag along for the ride, although Benny is inadvertently knocked off mid-ride. Bridget looks concerned, but Samson doesn't notice as the truck goes into the city.
The animals escape the truck just as it's about to compact its load, and work their way down the city streets. They're discovered by a poodle and two other angry dogs, who begin to chase them. The crew wonders why Samson doesn't just roar them off like he did in his past stories, but they manage to escape into the sewer, where they come across two street-wise alligators who help direct them to the port.
The "green box" is just being loaded up as Samson and the crew arrive at the port. They narrowly avoid being crushed by a container and manage to gain control of a small vessel, and begin chasing after the boat, but soon lose sight of it. Benny manages to fly in with the help of some Canadian geese, and they follow the boat to an African island. It's there that they discover that the "green boxes" aren't really transporting animals to the island at all. They're transporting them FROM it, as there's a volcano that looks like it's about to erupt.
Ryan escapes from the "green box" and runs away as he sees a bunch of strange animals approaching the box. Samson tries to give chase but manages to lose him somewhere in the jungle. He and his friends form a search party and begin looking, and happen upon an obnoxious animal with a big gas problem. The group sees Samson tempted to eat him, but he lets him go, and they begin wondering why. It's here that Samson confessed that he in fact did not come from the wild, but rather the circus, where he tried to stand up to a mechanical wildebeest but couldn't find the right roar to counter it, leaving the audience laughing. His father sends him away in shame. Samson runs off, leaving the crew on their own.
Soon, a group of wildebeests show up and snatch Nigel, Bridget, and Larry, and take them to the volcano, where the evil Kazar (William Shatner) is lamenting an evil plan to get revenge on the carnivorous animals above him- lions. Well, that and choreographing a dance number with the wildebeests. He has mistaken Nigel for "the One", a god that will lead them. It turns out one of the stuffed koala from the zoo fell off a biplane and managed to land on the island, saving Kazar from an attack by young lion cubs previously. Two vultures show up and notify Kazar that two lions are on the island, and Kazar immediately orders their capture, putting his plan of revenge in motion.
Samson looks around for his son and begins seeing strange visual discolorings in the atmosphere. He manages to finally find Ryan after much searching, but they soon find themselves facing off against a large number of wildebeests. Samson and Ryan are able to climb up a tree, and Ryan is curious as to why he's not mauling the wildebeests. It's here that Samson tells Ryan the truth about where he comes from, and Ryan is shocked. Shortly after, the wildebeests knock down the tree, knocking Samson off a cliff and taking Ryan back to the volcano, where he's reunited with the others. Kazar is upset the older lion wasn't brought back, but asks to prepare a sacrifice anyway.
Benny goes down to check on Samson and begins to wake him up, and here it's revealed who's given him the visual hints- a group of "covert" chameleons that can change color on command. They climb all over Benny and change the color of his skin, and soon render him invisible. This gives Samson an idea as to how to sneak into the cave to rescue the others.
The sacrifice is near-prepared, and Kazar is about to begin the proceedings, but Nigel attempts to stall by bringing up certain provisions, trying to keep his friends out of hot water. Soon, he begins floating about, with the wildebeests looking on in awe. This allows Benny to get the others to safety. It's soon revealed with some volcanic steam that the chameleons are making Samson invisible, and a face-off between Samson and Kazar begins. During the battle, Kazar is about to get the upper hand, shoving Samson towards some lava, but his friends have launched a "trick play" that launches Ryan right at him, growling with the roar he's been looking for. This allows Samson to get the upper hand, tearing off one of Kazar's horns and knocking him down.
The other wildebeests approach, but they've sided with Samson and Ryan, insisting that his choreography and leadership are nothing special. Kazar says he'll finish Samson himself, and Samson lets loose with an incredible roar that incapacitates him. Soon, the volcano begins coming down, ready to erupt, and the animals manage to escape, leaving Kazar to perish under falling rubble. They load up into the boat and manage to shove off just as the volcano erupts.
Happy that they've managed to survive, the wildebeests begin breaking out into song while Samson and Larry steer the ship. Benny begins to accept that Bridget will never be his girlfriend, but she surprises him by planting a big kiss on him. Nigel finds the stuffed animal that was confused for a god and kicks it overboard. Samson runs up and tries his own hand at dancing, and, despite looking awfully silly, Ryan cheers him on anyway, proud of his dad. The movie ends with the animals dancing around on the boat as it sails back to New York.
It turns out that the "green container" that Ryan, Samson's young cub son, boarded is actually being sent to Africa not to ship animals there, but to pick up animals in danger, as they are on a volcanic island. Samson and his friends Benny, Nigel, Bridget, and Larry all get on board a small ship and chase after the vessel containing this container, but manage to lose Ryan when they get to the volcanic island.
They begin searching for him, but Samson gets separated from the group when he admits that he himself did not grow up in the wild, but rather a circus act where he dad basically sent him away because he could not growl like a real lion (sort of the same problem he's having right now with Ryan). The others are soon captured by a group of wildebeests led by the evil Kazar, who's just as concentrated on evil deeds as he is on dancing. They mistakenly figure that Nigel is their God, since a stuffed animal resembling him landed on the island years ago and saved Kazar from danger.
Ryan is captured, just as Samson has found him, and Samson is knocked off a tree down a cliff. Benny finds him and manages to get him back on his feet, and, with the help of some covert chameleons who can change colors on figures, they sneak into the cave where the others are being held. However, some steam in the volcano knocks off the chameleons, and Samson is revealed. His friends manage to get away from the group as Samson begins fighting off Kazar and his followers, but Ryan is soon launched (with the help of a "trick play" used for turtle curling earlier in the film) at Kazar, roaring and landing right on him.
Soon, the other wildebeests turn on Kazar, implying that his choreography isn't all that, and Samson roars him off with a mighty roar. Soon, the volcano begins fully erupting, and the other animals manage to escape as Kazar is left behind. Samson, his friends, and the other wildebeests manage to escape on the boat as the island is coming down, and they celebrate by bursting into song and dance. Benny is greeted by a big ol' kiss by Bridget, while Nigel throws the stuffed toy that Kazar found overboard. And Samson is happy that Ryan finally found his roar.