The Fighter - S4-E3
Revealing mistake: The Woman spectator at the boxing match is wearing an obvious 1970s fashionable floppy sun hat and dress, instead of an appropriate 1930s style.
Revealing mistake: The wall in Jon-boy's room 'jiggles' a bit as Erin is confiding in Jon-boy about Maryellen, indicating it's either a set piece or an office partition instead of an exterior wall.
Revealing mistake: When John Boy and the others are watching the movie being shot, a helicopter can be heard. This takes place in 1936 with The Abdication of Edward VIII, and there would be no helicopters around at that time. (00:25:20)