In 2015, Alok Menghrajani wrote a simple game, including a floppy disk bootloader to run it, that fit in a tweet. Now that the tweet length is double what it was then, he’s made a version that can be burned to CD.
perl -E 'say"A"x46422,"BDRDAwMQFFTCBUT1JJVE8gU1BFQ0lGSUNBVElPTg","A"x54,"Ew","A"x2634,"/0NEMDAxAQ","A"x2721,"BAAAAYQ","A"x30,"SVVVqogAAAAAAAEAF","A"x2676,"LMBaACgB76gfbgTAM0Qv8D4uYAI86qqgcc+AXP45GA8SHIRPFB3DTeYSEhyBSwCa8CwicMB3rSG/sHNFbRFJjAke9rrwQ","A"x2638'|base64 -D>cd.iso
The code is compacted into Base64, but you get the idea: a ludicrously yet ingeniously simplified game wrapped in a perl script that dumps it into an iso file to burn to CD. The game is ~64 bytes long.
See also: the tweet-length demoscene.