5. Belloq Swallows A Bug - Raiders Of The Lost Ark
As far as famous movie flies go, the one that appeared to crawl into Belloq's mouth in Raiders of the Lost Ark is up there with the one which was fused with Jeff Goldblum at molecular level.
During the scene where Indiana Jones attempts to ambush the villain and his Nazi entourage, a bug can be seen crawling across the bad buy's face and seemingly entering his mouth. Actor Paul Freeman doesn't even flinch the entire time.
While the insect landing on Belloq's face was entirely unplanned, the movie's effects team tinkered with the footage and left it in the final cut as a subtle joke. It turns out Freeman didn't swallow the fly. It buzzed off, but its escape was edited out because implying that the villain ate it is way funnier.