Commander Keen 4: Secret of the Oracle

Dopefish

Developer Tom Hall on the creating the infamous Dopefish (taken from the 3D Realms website):

"The Dopefish, upon reflection, is pretty much based on one of two little faces my brother, sister, and I would draw on everything. Except stuck on a fish. I guess they were sort of the emoticons of the seventies. And of course, he's inspired by the Ravenous Bugblatter Beast of Traal from The Hitchhiker's Guide to the Galaxy. That's why they're the SECOND dumbest creature in the universe."

Eat Your Veggies

The song "Eat Your Veggies" in the Well of Wishes level actually was written for Commander Keen: Keen Dreams, but was removed from that game to save disk space. Explains the name, now, doesn't it?

Graphics

There was a special version released specifically for CGA, as the EGA/VGA version didn't support CGA.

CGA Composite

In 2016 VileR released an unofficial patch that allowed the CGA version of the game to use the CGA Composite mode. This results in CGA 16 colors graphics, as opposed of the CGA 4 color graphics of the original release.

OEM version

The game was bundled with the Gravis PC Gamepad

References

The opening sequence (with the words floating by each other) is a parody of the opening sequence of the movie The Terminator. When you select "Return to Demo" from the options screen, the story that's shown is an obvious parody of the Star Wars scrolling text opening sequence

Information also contributed by Itay Brenner, Jimmy Sherril, Kirschsaft, Roedie and Tony Gies