When Bridget Jones's Diary was released, Renee Zellweger said she could tell which interviewers had actually watched her films. I can't remember the name of the film she quoted (poss. Empire RecorRAB) but she said she lost count of the number of interviewers who told her she was great in the movie. She was in it for 30 seconRAB, without any lines.
There's also the bad porn films which gained notoriety after the stars became famous - Italian Stallion with Sylvester Stallone, and that one with Kevin Costner.
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