Many years ago, I worked on a product that provided a bunch of old emulated games. We properly licensed them, but many of the license holders no longer had the original ROMs, ripping the game data off of some of the really old consoles was quite difficult, and the only ROMs available publicly were cracked copies with demo's added. That was the birth of the demoscene, which was awesome, but bad for us trying to legitimately provide these games. So we ended up cheating. We used the cracked versions of these games, but we always loaded the games from a state just past when the demo would play, making them look normal and legit. Thank God all those early cracks put their demos only at the start and not, like, between levels 1 and 2, or we'd've been screwed.
It would be kind of sad/funny if one of the games had a bad crack and the game itself was broken and not caught by QA. For example, Earthbound has one final check that would cause the game to freeze and delete your save at the final boss.
The crack for The Colonel's Bequest worked by hardcoding the RNG in the interpreter to always return the same number. This broke every random element of the game, which is undetectable on a single playthrough.
This is the case for many "cracked" DOS games. You can find archives that say "we checked all the games to make sure they're really cracked", but I obtained a copy of Spaceward Ho! from such an archive, and the developers had pre-defeated this assurance measure by not invoking the copy protection until several turns into the game.
I think this was the case for one version of King's Bounty: The Legend on GOG (not the current version it sounds like?), which had a bug where you couldn't talk to an NPC at one point when you needed to do so to advance the game. At least, I recall someone mentioning somewhere when I looked after encountering the bug years ago that this was an issue of a random crack posted to the net that someone (the publisher I'm guessing, maybe GOG or the developer) had applied to produce the GOG version.
