"Quick change" is a form of the Short Con in which the Hustler confuses a cashier into giving more change than they should. The most lucrative quick change technique is the "progressive", in which smaller denomination bills are thrust back at the cashier for consolidation into a higher denomination. "Here, give me a five for these ones." (then, while holding the five and the ones...) "Oh, wait. Go ahead and give me a 10. Let me see... one, two, three, four and five is .. yeah, a 10. Thanks."
If you were paying attention, that was five dollars becoming 10. A quick change artist can keep that rolling until he ends up walking away with a $100 bill.
* In the novel American Gods, Mr. Wednesday casually pulls a variant of quickchanging, involving a credit card as well as cash, on a gas-station attendant. The exact details aren't mentioned, however: Neil Gaiman once stated in an interview that he'd deliberately tried to obfuscate the details of the cons used in the book, to prevent anybody from trying to replicate them in real life. (Didn't actually work, though. One of the bigger cons in the book was successfully replicated by a Canadian fan, who walked away with more than $6,000...)
* An old Abbott and Costello routine does a quickchange variation relying on Abbott's fast talk and Costello's stupidity. "Could you give me two 10s for a five?"
* In the South Park episode "Scott Tenorman Must Die", the titular Tenorman pulls this one on Cartman. Tenorman really pays for it later.