Revealing mistake: When the Christians are being fed to the lions, we can see that when a lion "attacks" one of the men, the man is actually smiling and visibly playing with that wild animal.
Quo Vadis (1951)
1 revealing mistake - chronological order
Directed by: Mervyn LeRoy, Anthony Mann
Starring: Peter Ustinov, Deborah Kerr, Robert Taylor, Leo Genn
Other mistake: When one of the Christians is being crucified and burnt, we can see that just after the man's "death" the body is substituted by a plastic doll covered in red paint.
More trivia for Quo Vadis