Tree Fiddy comes from South Park, in the 1999 episode The Succubus, where Chef's parents tell a rambling story about the Loch Ness Monster repeatedly disguising itself and asking for three dollars and fifty cents. The joke turned into a long-running catchphrase online, copied into forums, remixes and reaction posts whenever someone spotted a begging or scamming setup. Its staying power comes from the absurdly small amount and the idea that a legendary monster would work that hard for loose change.