The Ringer - S1-E1
Continuity mistake: When the Moblins attack Link in his room through a sort of trap door, the hole that is the door keeps changing locations, shapes, and the tiles around it all throughout the fight. Some points even disappearing entirely. (00:01:25 - 00:03:40)
Love 'Em and Leave 'Em - S1-E8
Continuity mistake: After Luigi says "Let's play cupid," he peeks around the corner along with Peach and Toad down at Mario going down the aisle with his "bride-to-be." Luigi, as expected, has been wearing green all episode, but when you see them peeking around the corner, Luigi's hat has become red. In the very next shot showing Luigi from behind, his hat has returned to green. (00:14:40)
Jimmy - October 14, 1964 - S2-E8
Factual error: The episode is set in 1964. When Frank and Jimmy first arrive at the dock and some of the dock workers are harassing Jimmy, there is a nice set of period appropriate cars in the foreground that the other dock workers are around, but in the background we see street traffic with 1980s cars driving by. (00:10:50)