Continuity mistake: When Selina returns home from work she takes milk out of the fridge and pours her cat some, leaving the carton on the worktop. She then runs to work, and when she returns after being changed to 'catwoman', the milk has vanished from the worktop. The dishes also move and plant pots appear on the window sill. (00:22:50 - 00:28:45)
Revealing mistake: In the final scene where the Penguin's corpse is dragged in the water by the other penguins, as he's immersed in, a sort of black mat floats away from the body, which was used to make the body drag easily.