While you are at the main menu press Up, Up, Down, Down, Left, Right, Left, Right, and Square.

Hot Cold level

Go to Level 14 and ride about half way through the level to find an alien crossing sign on the left hand side. Run into the sign and knock it over.

Eggipus Rex level

Go to Level 11 and take the yellow gem ride. Then proceed until reaching the area where the huge dinosaur chases Crash. Allow the second pterodactyl to capture Crash.