Every Litter Bit Hurts/As You Wish/Take a Hike - S1-E5
Other mistake: Take a Hike: When Lumpy is dragging the other characters on the stretcher, there is a wide shot with an animal's skull in the foreground. In the next shot, the skull has somehow moved behind the stretcher, and the stretcher is improperly overlapping the skull as well. (00:17:21)