Revealing mistake: When the sniper is shooting the cans, the close-up of the first can shows the metal peeling out as though the bullet had come from inside instead of outside.
Continuity mistake: When Steve Martin is working at the gas station, the Latinos come in with the stolen credit card and he puts the gas nozzle in the gas tank under the license plate. It is still in there when he hooks up the chain from the car to the church. But when he walks back from the church, the nozzle is mysteriously gone from the car, and has returned to the pump. (00:22:10)
Audio problem: During the duet "Tonight You Belong to Me" on the beach, Steve Martin is strumming the ukulele out of time with the audio, and he's not making the correct chord changes on the fingerboard. You can also see his mouth bungle the lyrics, although the overdubbed audio is fine.