Prehistoric Tale, A

On the title screen (player select, music, highscores) type "PLAY THE SPASEBO BLUES"*. The gradient select bar will turn from blue to red. This will give you access the following keys during play:

+ - Skip to next level
1 - Level 2 Warp - Egg Catching
2 - Level 3 Warp - Shoot the Dinosaurs
3 - Level 4 Warp - Slide puzzle
L - Add Lives
I - Turns the player invincible for a short period of time (turns invisible). Press any key but the 'I' to turn visible again
E - Jump to ending
G - Makes the score go up, but maybe something else
B - Set level to 100...complete the current level and complete the game

* it's "PLAZ THE SPASEBO BLUES" on German keyboards.

On the screen with the dinosaur, just before the title screen with the scroller, type "OOH CRIKEY" for an extremely long scrolling message.

[Source: Abaddon, via message posted on EAB]