Zoolander 

Sometimes actors forget their lines, but that can lead to incredible accidents. This is especially true if the supporting cast can improvise as well, which happened in the movie Zoolander.  

In the scene where titular male model  played by Ben Stiller, learns of the plot to use male models for political attacks, Stiller forgot his line. Instead of looking blankly at the camera, he just repeated the line he had just said, “Why male models?” Actor David Duchovny rolled with it and responded with, “You serious? I just told you that a moment ago.” It’s now part of comedy lore.