In the Hoodlum's factory, get to the place where you have to jump across crates to get to the other side. Once there, keep going up. You will eventually reach a location with a switch to activate the lifts to get to this second "conveyor belt". On those lifts, get pretty well up to the top. There is a hole in the side of a huge "pipe". Jump and helicopter over there and go in. You will see some of the villains from Rayman 2,, including Admiral Razorbeard and his other cronies.
