Continuity mistake: When Bart falls down the stairs, you see him fall down at least 50 stairs in the close up. There are never this many on the full shots of the staircase.
Continuity mistake: When Lisa arrives at Dr. Nick's, amongst the wheelbarrow line is a Professor Frink (and he's not even first in the cue). However, just a few minutes later, when Lisa ends up in the mud pit, we can see Frink amongst the crowd.
Continuity mistake: When Homer's Vegas wife shows him the video in front of Marge, it shows Homer kissing Ned. This didn't happen when she showed it in the Vegas episode.
Tree House of Horror X - S11-E4
[The Simpsons are driving down a road as fast as possible.]
Homer: Dear God, it's Homer. If you really love me you'll save my life now.
[The gas needle immediately drops to empty and the car stops.]
Homer: D'oh.
Trivia: The Simpsons holds the record for most guest stars; it is also the only non-variety show to have had appearances from three former Beatles (Paul, George and Ringo).
Question: Which episodes feature the "Howling Dog" (usually used on outside shots of buildings)?