Commander Keen: Goodbye Galaxy! is a platform game developed by id Software and published by Apogee Software in 1991 for MS-DOS.
The game is divided in two different episodes, numbered as the fourth, released as shareware, and fifth in the series, even if they really are the fifth and sixth episode (the numbering doesn't include Commander Keen in Keen Dreams). Initially the game was planned to be released as a trilogy, but during development the third episode was split off and released as a stand-alone game, named Commander Keen in Aliens Ate My Babysitter.
