Go to Jungle Japes and go to the place where you find the snail shell that Tiny can fall into (you get there through the tunnel that also connects to Cranky's Cabin). As Chunky, become Hulky Chunky and then run over to the shell. Try jumping at it, sliding into it. You will eventually fall through. sometimes you will end up inside the shell and other times you will end up at some other area in the level.