Revealing mistake: When the cat rips the painting, it is already damaged before it touches it.
The Man with Two Brains (1983)
1 revealing mistake - chronological order
Directed by: Carl Reiner
Starring: Steve Martin, Kathleen Turner, David Warner, Paul Benedict
Other mistake: Steve Martin, a surgeon, never once wears a surgical mask while performing any operation.
Dr. Necessiter's butler: Can I get you anything more, doctor? I'm about to retire.
Dr. Michael Hfuhruhurr: Really? You seem so young.