The game Creatures 2 on the Commodore 64 had an unusual cheat to get infinite lives which unlike most things on the Internet that are said to "really work" really worked!
What you had to do was lick your finger and then rub it on the joystick port. IIRC A picture of a mouse (I believe he was a character from another game) would appear which would flap his arms as you rubbed the port, and eventually he'd turn grey to indicate the cheat was active.
I know it sounds weirdly perverted, but it actually did the trick!
My question is, how?