The Action Replay Cartridge was amazing utility cartridge at the time.
So many features in one package: a Fast load, reset button, Code monitor, Sprite monitor, Screen dump, Program compactor or fit more games on one disk and more. But the reason it is here is because of the “Memory Snap Shot” feature. This would copy what ever program was running in memory and save it to disk.
This was awesome for the removing copy protection from so many programs. Just load the game from the original disk. This will pass all start up copy protection, hit your snap shot button on the title screen, save it and like magic you now have a copy protection free program. This could later be defeated by have multiple or delays copy protection checks.

LINK to my VIDEO of me using the Action Reply
https://www.c64copyprotection.com/action-replay-to-by-pass-protection/