Not sure are you referring to this ?

SECRET Secret Levels

There are two secret levels in the game that I don't think you can access until you beat the game.

The first: Hot Coco, which can be accessesed through Road Crash. When you see the sign that shows an alien head, hit it and you will be transported to Hot Coco.

The next: Eggapus Rex, is accessesed by going throught the yellow gem path on Dino-Mite! When your running from the triceratops, let youself be taken by the second pterodactyl. You will be transported to this cool level.