Commander Keen Series

—Mild cheats:
[C]+[T]+[Spacebar] : Free items
[F8]          : Some funny stuff.
[G]+[O]+[D]      : God Mode
[Shift]+[Tab]    : End level
—Hard cheats:
Add to the commandline (for series 1-4):
NOWAIT
(This also removes various delays and nagscreens)
Then, in the game, use [F10]+ some letter keys :
[W] Warp to level     [E] Restart
[T] Sprite test       [Y] Mess up sprites
[I] Free items       [S] Toggle slow motion
[D] Record demo       [G] Toggle God mode
[J] Toggle jump cheat   [C] Stats
[V] Add VLB’s         [N] Toggle clipping
[M] Memory usage
You may also try adding TEDLEVEL, COMP, NOCOMP.
—Secrets:
Episode 4:
In the “Pyramide of moons” get the yellow gem and
open the door then get all of the 12 worms in one
place and they will turn into
a foot climb the foot and enter the secret level.