Earth

The Earth as it appears in Keen 1

Earth is the planet where both Commander Keen and Mortimer McMire are from. Keen still lives on Earth, but it is difficult to say how much time Mortimer spends on his home planet. At some point, Mortimer was directing the Vorticons towards Earth in their Vorticon Mothership and almost made them destroy some of Earth's major cities (see the Keen 2 Story), but Keen was able to stop them in time.

The Bloogs also briefly stopped by Earth to kidnap Keen's babysitter in Keen 6: Aliens Ate My Baby Sitter!, under directions from Mortimer McMire (see Keen 6 Story).

For details not related to Commander Keen's plot, see Earth (Wikipedia).