Give Me Something Good to Eat - S1-E2
Revealing mistake: When Chucky is walking around on the street in the "Hello Kitty" mask, you can tell it's someone in a costume, primarily because you can see a little bit of their (very fleshy) neck at the bottom of the mask a few times.
Revealing mistake: Pretty much throughout the whole show, the iron prison doors do not have any way to lock. Guards put the key in, but there is no actual lock or latch on either side of the door. Even when these doors are pushed shut, there is not a locking sound.