Complete the game 100% to get a new ending. Alternately, defeat Cortex with 44 gems and 30 Sapphire or better relics and you’ll get a different ending.
Secret Level: Epigus Rex:
Go to level 11, Dino Might, and go into the gold gem path. Follow the path until you get to the pterodactyls. Pass the first one and, when you get to the second one, jump into it to be transported to a level where you ride the dinosaur through the entire level.
Secret level: Hot Coco:
In the "Road Crash" level there is a sign on the left hand path that has a picture of an alien on it. If you run it over, you will reach level 31,a secret level.
Unlockable "Relic" Levels:
Access the following levels by obtaining the corresponding number of relics:
LEVEL - RELICS
Level 26 (Ski Crazed) – Collect Five Relics
Level 27 (Hang’em High) - Collect Ten Relics
Level 28 (Area 51) - Collect Fifteen Relics
Level 29 (Future Frenzy) - Collect Twenty Relics
Level 30 (Rings of Power) - Collect Twenty-Five Relics
Go to the level entitled Makin’ Waves and obtain the Clock item. About a quarter of the way through you should see a ramp and a guy in a rowboat. Go on the ramp and land on him to get two lives. However, you must kill your character to keep getting more lives. Since you get two at a time, you can slowly but surely build up your number of extra lives. Remember; get the Clock item, get the lives by jumping on the guy in the rowboat, kill your character, and repeat.