Revealing mistake: In the scene where they're tumbling down the hill, Buttercup has a beard.
Continuity mistake: In the scene were Johnny is fighting Robbie, his belt breaks, and is hanging down. Next shot it is fastened again. And then it is hanging down again. (01:11:45)
Visible crew/equipment: Loretta calls for Ronny at the bakery, and when he picks up the phone then promptly hangs up on her, the dark protruding outline of the microphone wire is visible at his right side. It happens again when Loretta visits the bakery and Ronny tells her Johnny took his life from him. Additionally, later when Ronny and Loretta spot each other at the fountain in the Lincoln Center Plaza, there appears to be an actor's mark at Ronny's feet. (00:25:00 - 00:27:05)
Continuity mistake: When Molly Ringwald is on the phone at the club and gets approached by the girl in orange, throughout the whole conversation the position of the phone receiver in Randy's hand is wildly inconsistent. (00:09:30 - 00:11:00)