Continuity mistake: Kimmy Keegan gets new Mode business cards and asks Betty what her cards say. Betty says she doesn't have business cards. But in 1-4, "Fey's Sleigh Ride" Betty is given business cards and hands them out at a bar.
In episode "Fake Plastic Snow," when the Polaroid photo is shown of Betty and Walter with his boss and his wife, Betty's hands are behind Walter and the boss's wife's back. When it was taken, her left arm was out and her hand was on her own leg.