The story
Coined in The Simpsons 1993 episode "Homer Goes to College" in which a group of naive nerds willingly give their wallets to a thief identifying himself as "the wallet inspector".
Etymology from Wiktionary, CC BY-SA 4.0.
wallet inspector
Today it means: One who takes advantage of the naïveté of another, particularly if the ulterior motive appears obvious. Full definition →