Revealing mistake: When Hymie is investigating the unconscious man in the shower, for some the reason the man is wearing underpants even though he is in a shower. Evidently for modesty.
Revealing mistake: When Purvis is about to go onto the field, it cuts to a close up of Purvis' face and you can actually see folds in the fake sky behind Purvis.
Revealing mistake: When Hymie does the high jump, when the film cuts to a shot of him clearing the bar, Hymie's hair is curly when it should be flattened down like when he took of and as he landed. It is obviously a stunt double.