Plot hole: When Connie uses the wish machine to make Malloy small again, she instead wished for Ethel's breasts to get significantly bigger. However, in the next scene Ethel's breasts are back to her regular size. The plot shows that the wish doesn't wear off, and someone else would have needed to wish for Ethel's breast to get smaller but no one did.
Old Wounds - S3-E6
Continuity mistake: Steve brings Denzel a McRib sandwich and says don't ask how I got it. He shows Denzel his "purple" hand. When Steve takes the sandwich back, the purple color completely vanishes without him wiping it off.
Continuity mistake: When Woody pulls the lever to shock Steve, right before Steve sees the global warming disaster, he breaks the handle and it's in the up/on position. After the vision, in the wide shot, the handle is no longer broken and in the down position. In the next shot it's back up and broken.
