Cadillacs And Dinosaurs 
Level select:
Pause game play, then press C, Up, B, Right, Up, B(2), A, Down, Up, B(2), A, Down, Up, B. Press A + B + C + Start and return to the main menu. Press Left or Right to select a starting level. 

Extra life:
Pause game play, then press C, A, Down, A, Left(2), A, C. A sound will confirm correct code entry. 

Extra time:
Pause game play, then press A, C, A, Down. A sound will confirm correct code entry. 

Easy mode:
Pause game play, then press C, A, Right, B. A sound will confirm correct code entry. 

Poacher yell:
Note: This code requires a six button controller. Pause game play, then press C, A, Down. Then, press Mode during game play to yell.