Friends with Burger-fits - S5-E3
Continuity mistake: After Mike and Mort warn Bob about the 5-lb burger at Dusty's Feedbag, Bob rushes out to save Teddy from himself. When Bob arrives and opens the restaurant's doors, there's a variety of condiments on Teddy's table in the wide shot, but in the next close-up, all the condiments have vanished.
Continuity mistake: When Jimmy Jr. Comes up to Tina, Gene's lunch tray has no hot dog or milk, but when it cuts to the other angle, there's now a hot dog and milk.
Itty Bitty Ditty Committee - S5-E17
Continuity mistake: Gene's keyboard has a set of 3 black keys on both ends. But in the flashback when he's in bed with it, the end has a set of 2 black keys.
Continuity mistake: In a scene after Teddy shows up at Helen's house, but before Helen arrives, Louise uses a picture of Helen to show that Helen has the look of a killer. In the close-ups, when the family is covering various parts of the picture, Helen has a closed mouth smile, but in subsequent shots Helen has an open-mouthed smile.
Answer: S04e15, "The Kids Rob a Train."
Bishop73