Mine comes from a pretty distinct memory when I was around 6~7 years old.

There used to be an Asian market that we'd frequent which had a small arcade corner to distract the kids while the parents did their shopping, and, for whatever reason, one of the games they had was a Mortal Kombat II cabinet. Most of us kids there were pretty shit at fighting games, so matches there were mostly cheesing each other with projectiles and nobody had figured out how to do fatalities. Until, that is some older kids showed up one day and began cleaning house. One of those older kids always played Johnny Cage and always did the Triple Decapitation fatality whenever he played against female characters. Once I witnessed this as a kid, the rest, as they say, is history.