Continuity mistake: When Mario, Toad and Luigi are driving to the rebel fort, the seatbelts they are wearing disappear for most of the scene. (00:17:30 - 00:18:40)
Two Plumbers and a Baby - S1-E17
Continuity mistake: In one scene, Luigi is wearing the same color hat as Mario and when Luigi opens his mouth to talk, it's Mario's voice we hear.
Robo Koopa - S1-E52
Continuity mistake: When Luigi crawls out of the remains of the Plumbernator warsuit, his face is still in the unit of where it was when he was in it, even though he's outside of it right now. (00:11:40)
Love 'Em and Leave 'Em - S1-E8
Continuity mistake: In the scene where the Princess first has the idea for getting another love potion, the spots on Toad's head change to black then back to red. (00:14:12)
Raiders of the Lost Mushroom - S1-E49
Continuity mistake: Near the end, when Koopa escapes through the warp you will see, for a split second, that Mario and Luigi have switched their colors. (00:38:15)
Continuity mistake: The Thunderbirdo is supposed to be pink. It is green when first visible after Koopa orders it up. It turns green again right before it explodes. (00:19:15 - 00:23:55)
Continuity mistake: When Mario, Luigi and Toad say goodbye to the Princess, Toad is standing at the front of their car, Luigi in the middle, and Mario at the back. Two shots later, the order changes to Mario at the front, then Toad, and Luigi at the back of the car. (00:15:10)
Continuity mistake: After the Marios say goodbye to the Princess, Mario is at the front of their car, then Toad, and Luigi at the back. Mario and Luigi swap places for the rest of the scene. (00:15:15 - 00:16:10)
Continuity mistake: When Koopa sends Mouser to hunt down the Marios after finding out they've escaped, the binoculars that he was holding have disappeared. (00:17:55)
Raiders of the Lost Mushroom - S1-E49
Continuity mistake: When Koopa escapes through the warp at the end, the hole closes up. When Mario says "We sure whipped him this time," (meaning Koopa) look at the ground and you will see that everyone is standing next to the wide open hole. (00:38:25)
Robo Koopa - S1-E52
Continuity mistake: Koopa manages to take Toad and the Princess hostage by surrounding them in electric force fields so they can't move. These force fields disappear when Koopa starts chasing Mario, Luigi, Bunsun and Dr. Nerdnik. (00:05:50)
Robo Koopa - S1-E52
Continuity mistake: During the fight, the egg stains on Koopa either disappear or move around him. The stains eventually disappear entirely. (00:10:40)
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)
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)
Robo Koopa - S1-E52
Continuity mistake: During the fight sequence, Koopa ties a rope around the Plumbinator's metal body and pulls the Plumbinator over to him. Luigi cuts the rope with a pair of scissors, causing Koopa to fall back. The part of the rope tied on the Plumbinator disappears for the rest of the scene. (00:10:50)
Robo Koopa - S1-E52
Continuity mistake: When Koopa brags about his vision, toes, etc, when his goggles come out, the two eyepieces are on his right eye for several frames, then it suddenly changes to both eyepieces on both eyes. (00:02:15)
Robo Koopa - S1-E52
Continuity mistake: When Mario, Luigi, Bunsun and Dr. Nerdnik are about to be crushed by the electric pole, when Luigi moans "we're doomed," he is in front of Mario. In the next shot, Mario is looking ahead while saying "doomed, schmoomed." In this same shot, Mario pulls Luigi over to a nearby fire hydrant, and Luigi moves onscreen from Mario's right. Therefore, Luigi has changed position. (00:07:10)
Robo Koopa - S1-E52
Continuity mistake: At the beginning of the shot, where Dr. Nerdnik builds the Plumbinator, the Mario Bros. change positions, even though they were standing the whole time. (00:08:00)
Robo Koopa - S1-E52
Continuity mistake: The Plumbinator is light blue. It changes to a darker blue when Mario says "May the best machine win" to Koopa. (00:10:05)
Robo Koopa - S1-E52
Continuity mistake: As the fight between Koopa and the Plumbinator begins, in one shot the camera zooms in to Koopa while under the Plumbinator's legs. Robo Koopa's color is light blue in this shot, when it is dark blue in the rest of the episode. (00:10:15)