Press Start, Select to play a level that already has been completed.
Bonus Levels
Kill all the small dinosaurs before cracking the red egg in the middle of level 8. A bonus level will begin where your weapon may be powered up. The bonus level also contains a key that allows entry to the blue dots on the map. Another red egg that leads to a bonus level is at the beginning of level 9.
Max Lives
Return to a level that contains an extra life after completing it once. Take the extra life and press Start, Select to end the level. Repeat this procedure to accumulate extra lives.
Extra Lives
Collect a key to go to the first blue spot. Collect all the meat and wait for the extra life to drop, but do not collect it. Wait at this location and four more extra lives will drop down.