So Then a Bat or A Monkey - S1-E1
Revealing mistake: When Joel puts the dead body in the freezer, the eyes are open. When he pushes the head to the side so he can close the lid the body plainly closes his eyes.
Revealing mistake: We see George hit some trash cans while driving, then a while later later he hits some different ones. However the clip we see the second time is the first clip, reused.
Revealing mistake: When Andi walks into the library (this is not Andi's dream) it cuts to the librarian sitting at her desk and we can see the shot is flipped - note the bookcase and the librarian's buttons. (00:10:40)