/vr/ - Retro Games

What were some of the more interesting or outlandish forms of copy protection/anti-tamper for cheating in retro games? I know of Earthbound's incredible lengths to fuck with players if it thought it was a bootleg, but are there any others that are particularly noteworthy, either in what they do or how they preform their checks?

Pic related is a King Quest insert that came with the manual, allowing you to bypass the copy protection when starting the game.