Ah, Tetris. I remember stripping out the copy protection from the MSDOS version with a debugger. Not because I wanted to resell it, which would have been difficult back then, just because I found it irritating.

I also added mouse support, once again using a debugger, for Hercules Graphics to a wargame - it was the ever popular Battle of the Bulge, by a famous designer who's name I can't remember. Guy that did Eastern Front on the Atari.

Edit: Chris Crawford