Wikidipedia says ...

Not long after Polokus - god and spirit of a newly created planet where the game takes place - departs, an army of Robo-Pirates led by Admiral Razorbeard takes over and enslaves the planet, holding the captured inhabitants in the pirate prison ship, "The Buccaneer".

Eventually Rayman and his friends are captured, but with some help from his best friend Globox they escape, but get separated in the process. As he progresses along in search of help from Ly the Fairy, he learns that the pirates have broken the Heart of the World, the world's core, into 1000 lums that have then been scattered all over the planet, weakening the world as a result. It's up to him and whatever help he can get to collect these lums but more importantly, retrieve the 4 legendary Masks that are said to awaken the Great Pokolus, the planet's greatest hope to exterminate the Robo-Pirates and once again liberate the World.

After escaping and not being able to find Globox, he meets the teensies who have forgotten which one of them is the teensie king and squabble over it.

Rayman later meets Clark who has a bellyache from chewing a robo pirate in battle and must go to The Cave of Bad Dreams to get the elixer to heal him.

I say ...

This is a must have. Everyone who makes games should play this game from start to finish - the level design, graphics and ambience is absolutely incredible. I can't ever recall playing a game with such intuitively designed levels and so polished in collisions, flow and 'feel'.

I can't gush about this game enough ... it really is an inspirational game and one that serves as a great lesson on camera, cinematics and general game mechanics for anyone serious about making games.