Continuity mistake: When the crocodiles approach the general store, the store's front door has its doorknob on the left, but in the next shot, it appears on the right. (00:06:26)
Continuity mistake: When the ketchup lorry crosses the bridge, it has a cream cab and a red trailer, but in the next shot, it has a blue cab and a grey trailer.
Revealing mistake: When the camera pans across the front of Double Cross Ranch, the edge of an animation cel is visible. (00:13:51)
Revealing mistake: When a front view of King Koopa running down a street is shown, he clips through a building. (00:15:25)
The Koopas are Coming! The Koopas are Coming! - S1-E35
Continuity mistake: Just before the pillory is destroyed, it is violet, but in the next shot, it is orange. (00:14:37)
Audio problem: When King Koopa throws the snake at the Mario Bros., they use Luigi's voice when King Koopa says "Quick, quick! Run away from him!"
Continuity mistake: This mistake is in the intro with Mario and Luigi in real life. When Mario breaks the ceiling while Bowser is holding a yellow bar, Mario's gloves disappear from his hands when he jumps to break the ceiling. When he lands, his gloves reappear back on his hands. (00:00:26)
Revealing mistake: When the camera scrolls to Grunt (in the scene where the gang are locked up in a cell, being watched a strong, non-human security guard named Grunt), he appears out of thin air. The animators might have had some trouble putting him into the scrolling shot. (00:11:15)
Other mistake: In many of the live-action segments, the Alarmtron logo on the alarm in the Mario Bros' residence has been partially covered to read "Acarmtron" instead. In addition, in several episodes, the phone number for Alarmtron is also partially covered.