Star Koopa - S1-E51
Revealing mistake: When Obi-Wan Toadi presents the pizza to Mario, the right strap of Mario's seat is connected to thin air. This also happens when he says that the pizza will bolster his appetite. (00:14:48)
Robo Koopa - S1-E52
Revealing mistake: In the first chase scene, the backgrounds are usually repeated in close-up shots, because you can see a sudden jump in the background animation. (00:00:40 - 00:02:25)
Robo Koopa - S1-E52
Revealing mistake: When Bunsun walks up to Dr. Nerdnik to free him, an animation mistake is noticable. Bunsun is far away and she walks up to him, and during this whole sequence her body is in front of Dr. Nerdnik, according to the camera's view. (00:04:55)
Robo Koopa - S1-E52
Revealing mistake: After Robo Koopa asks how to stop his suit when it malfunctions, he moves without moving his legs. (00:05:10)
Robo Koopa - S1-E52
Revealing mistake: When Mario and his friends run, as they fight off Koopa's minions, Luigi runs in midair. (00:07:12)
Robo Koopa - S1-E52
Revealing mistake: When Robo Koopa bursts out of the workshop, he is briefly layered over a wall. (00:08:49)