I recall reading that at one point game programmers were using portions of their code as textures. Which reminds me of the story of Mel. http://www.catb.org/jargon/html/story-of-mel.html
One part of it would repeatedly read one "weak" sector that had been incorrectly encoded on the disk in such a way that it would usually read inconsistently, and would crash the game with an obscure system error if it didn't read differently.
Cute, but kind of a problem when you have a much better quality floppy drive which read the weak sector consistently.
Stenography via rearranging executable code within a binary file so that the binary file looks most like a particular bitmap.