It's been 14 long years since our second Keen trilogy but these ended up being the best Keens of all. Unfortunately, we had a publishing deal that forced us to release one of the three Keens at retail thus breaking up the sacred trilogy of games which resulted in lower sales of this second trilogy.
The retail game was called Aliens Ate My Baby Sitter! (it was numbered Keen6) and stood on its own. Then the game duo we called Goodbye, Galaxy! had Keens 4 and 5 in it. Keen 4 took 3 months to develop, then we made Keen 6 in order to get it in the stores for Christmas and that took 2 months to make, and finally my favorite Keen, Keen 5, took us only ONE MONTH to develop. Apogee Software released the duo into shareware on December 15, 1991 while Keen 6 was in the stores.
You can see the second-oldest id Software logo on the Keen 6 box. The oldest id logo was in the help section of the original Keen 1-3 games. The "Lost Keen" came before the two Keen trilogies and was called Keen Dreams and was published by Softdisk in May 1991.
Anyone paying close attention to the Keen series will see some interesting parallels between the two trilogies. Both Keens 1 & 4 take place on friendly planets, Keens 2 & 5 take place docked onto an alien spaceship, and Keens 3 & 6 take place on hostile alien planets.
If you look closely at the Keen 5 title art you'll see Keen running away from a Robo Red but through the window of the space station you can see the secret level on the surface of the planet.
When we were developing Keens 4-6 we were living in Madison, Wisconsin in the freezing winter and worked constantly because it was so awful outside. Cops were frequently busting down the doors next door. It was such a bad neighborhood that we were basically developing our games out of a crackhouse!