Star-Crossed - June 15, 1972 - S1-E3
Revealing mistake: Sam stares at himself in the mirror and takes out his wallet to determine who he's leaped into. But the "reflection" in the mirror lowers the wallet and looks back up before Sam does. (00:05:20)
Revealing mistake: While Link is sword laser zapping the first two Tin Suits, one shot shows a house behind Link. The door on that house looks like it was rushed when it was drawn or the whole house was. There is a window that looks normal enough, but maybe slightly on the large side. But right below the window, there is a door that is way too small. It looks ridiculous and out of place, especially when compared to the window. (00:31:00)
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)