While playing the Bigfoot Mountain level, go straight at the start. You will see a house. Shoot the snowman to unlock Andre Latoilette.
While playing the Bandito Attack level, go around the course and look for a movie star. Shoot him to unlock Atomic Johnny.
While playing the Coyote Canyon level, in the cave look up at a purple thing. Shoot it and go up. Look for an unlock signal to get the Bandito for race and dogfight mode.
While playing the Coyote Canyon level, go down to the cowboy town. Look for a girl that is going to be hung. She is Cactus Rose. Shoot her to unlock her.
While playing the Danger Island level, in the jungle area fly by or shoot the snake on the vine to unlock Island Jack.
While playing the Thugsville level, shoot the box with the British flag located under the bridge on a ship in the dock to unlock Margareta Basher.
While playing the Torpedo Run level, look on the radar. There will be two blips. Go left and shoot the yellow submarine to unlock Professor Guntentaag and Sven 209.
While playing the Thugsville level, fly into the first train tunnel and get the unlock signal to get the Purple Gremelin for race and dogfight mode.
While playing the Cave Of Blunders level, fly down near the ground. If you see a big man in black who is trying to kill Sheik Abdul, shoot the killer to unlock Sheik Abdul.
To Unlock Everything enter: Zenbu