For me it was downloading Quarantine that i originally had in 1994 on 3DO. Not the game so much, just that i totally forgot copy protection was done via physical codes back then.

here's how it looked, for example the game would give you a Weight and MPH value and you'd have to supply the 3 digit number that corresponds

https://archive.org/...

"This a scan of the "Red Card", a copy protection scheme for Quarantine. This was black text on a deep red background that was hard to copy by black and white copiers of the era. Color copiers, which cost about a dollar a page had to be used. "