Why do bills travel in envelopes?

This little gem of a joke pulls a classic bait (Review)-and-switch using the word "bills." The setup primes your brain to think about invoices—those delightful paper reminders that your money is about to go on a trip. But the punchline cleverly flips the script, personifying dollar bills as helpless travelers who need a little paper companion to get around. The humor comes from the absurd mental image of a lonely five-dollar bill needing an envelope as its personal chauffeur.

The joke taps into the once-universal experience of dealing with snail mail. Before the magic of online payments, paying an invoice meant the familiar ritual of writing a check, sealing it in an envelope, and sending it on its way. This gag playfully mashes that reality together with the physical nature of cash itself, treating our money like it has a mind of its own and can’t quite manage to get to the utility company without a proper escort.