Revealing mistake: When Tommy and her boys are roughing up Randolph in Angie's apartment, Tommy throws Randolph across the room into the piano. The vase sitting on top of the piano falls before Randolph ever touches the piano. Seen better in slow-mo. (00:57:20)
Revealing mistake: The Bears' bus is driving by a green highway sign reading something like "Nutville 2". Road signs are normally made of something rigid. But as the bus passes, the sign ripples in the breeze, and you can tell it's just made of fabric or plastic.
Revealing mistake: If you look closely at Billy Flynn in the musical number "All I Care About is Love", right at the end when he takes off the boxers, you can see that he is wearing underwear underneath them.