Today marks the 25th anniversary of the release of the original Commander Keen in 1990. There's a pretty extensive article on the history of the platformer on Wikipedia explaining the franchise's place in history: "The cartoon-style platform games are notable for their pioneering use of EGA graphics and shareware distribution, and they were some of the first games by id Software (who went on to later develop Wolfenstein 3D, Doom and Quake). The games were also exciting to the PC gaming community of the time because of John D. Carmack's smooth-scrolling graphics game engine." On a related note, John Romero has uploaded a video of a Super Mario Bros. 3 PC Demo (thanks Gamasutra) showing a prototype game developed by a prototype of what would soon become id Software, and the guts of this project eventually became Commander Keen. Very keen Keen designer Tom Hall a Facebook post celebrating the occasion with a new tribute level created for Super Mario Maker. He concludes with a plea to rights holder Zenimax to release the IP or at least the source code:

LET’S GET SOME KEEN ON EVERYBODY! And ZENIMAX, it’s been 25 YEARS. Can I have Keen back? (grin emoticon) Well. doesn’t hurt to ask. At LEAST release the Keen 4-6 source, okay?