What's the most egregious thing an extra has ever done in a movie?

The “I think it’s across the Bay, in Alameda” lady in 1986 San Francisco in Star Trek IV: The Voyage Home. From IMDB:

The woman who answers Uhura and Chekov when they are looking for the nuclear vessel was Layla Sarakalo, an extra who had never acted before and was not supposed to speak much. Sarakalo happened to be on the set when her car was towed away to make room for the film's production. She then offered to be an extra, because she needed the money to get her car back. She was told to "act naturally", and when she was asked, she improvised an answer. Much to her surprise, her unscripted line was kept in the film. This was because director Leonard Nimoy enjoyed the spontaneity of the scene so much that he left it the way it was.

Also, in order to keep her line in the final film, it was necessary for Sarakalo to be inducted into SAG-AFTRA.