Easy for You to Sleigh/Whishy Washy/Who's to Flame - S1-E4
Continuity mistake: Easy for You to Sleigh: When Lifty and Shifty break into Pop and Cub's house, Shifty places his sack on the ground. Then, when they both run over to the Christmas tree, Shifty doesn't take the sack with him, and he still doesn't have it when they leave the house. However, when they both arrive at Mime's tent, Shifty has the sack again. (00:01:40 - 00:02:48)