After Batman is deceived and gassed by Milo and Romulus, Romulus takes away his utility belt. After that, when Batman is chained to the ground in the area outside of Milo's cabin, he is wearing his utility belt again. Once he confronts the werewolf, he still has the belt. There was no reason Milo and Romulus would put his belt back on again.
In the few seconds and frames it takes Romulus to transform back into a human back at the hut, Dr. Milo's clothes change every couple frames from gray pants, a blue shirt, and a lab coat to gray pants, a brown jacket, and a blue shirt, and back again.
For one frame during the final battle with the werewolf, the logo on Batman's chest is black and white instead of black and yellow.
During Anthony's flashback, when we seem him riding a car, the eye animation of his girlfriend is messed up, so for a couple of moments, she has multiple eyes on the side of her head.
A sign on an exhibit at the zoo is incorrectly spelled "LEPORDS".