1989-91 MS-DOS computer game series. Played today in the DosBox emulator. Reached its apotheosises with NETKEEN.

List of official commander keen games:

Commander Keen 1: Marooned on Mars

Commander Keen 2: The Earth Explodes

Commander Keen 3: Keen Must Die!

Commander Keen: Keen Dreams

Commander Keen 4: Secret of the Oracle

Commander Keen 5: The Armageddon Machine

Commander Keen 6: Aliens Ate My Babysitter!