Bazooka the Gem
The red gem is very difficult to acquire in the "Crash and Burn" level. This is due to a large gorge that requires you to long jump, then slide, then double jump and finally spin to make it across. Instead of going through this process, shoot your bazooka at the red gem to obtain it. Jump into the gorge to die and you'll be transported to the last checkpoint. You can finish the level from this point, avoiding the gorge route.
Extra Life Mammoths
When you defeat the second boss, you'll earn a new skill, the double jump. Play the "Arctic Antics" level again and head towards the three woolly mammoths that you passed the first time you played through this level. Use the double jump ability to land on their heads; you'll receive one extra life for each mammoth.
Elementals Trick
When you're battling Crunch, he'll release Elementals, which are evil masks that can control the four elements of fire, water, earth and air. These can be difficult to fight, but you can avoid the attacks of two of the Elementals. Wa-Wa controls water, so dodge its attacks by staying at the bottom of the screen where the water balls can't get to you. Stand in the metal area when you're fighting the air-controlling Lo-Lo, and its attacks will never touch you.
Miscellaneous Cheats
Begin a new game and enter "wombat" when you're asked for your name; this will unlock all of the game's levels. Gather all of the 46 gems spread throughout the game to watch the alternative ending when you complete the game. Pause the game quickly when you die. Choose the "Warp Room" option from the menu and Crash will be transported to the Warp Room without losing a life.