Other mistake: The Time Expansion Helmet was supposed to allow Dexter to perform his 30 minute morning task in 30 seconds. Since this is the case shouldn't the cat have hit the fishbowl ages ago as time is not frozen.
Other mistake: In the closed-captioning, when Arnold and Gerald "touch thumbs" (and you hear that "sproing" sound), the caption says "[glass shatters]"
Monkey Fun - S2-E13
Other mistake: Season 2 episode 13 "Monkey Fun": Just before the enlarged Titano appears at the zoo, there is a family watching normal-sized monkeys in a cage. The family father (farthest on the right) has a drawing disorder with his eyes: their pupils look up and down, respectively, giving him a rather goofy expression.
Blue Wants to Play a Game - S1-E12
Other mistake: The jigsaw puzzle Steve and Blue help Shovel and Pail with has a picture of everyone playing musical chairs from the Mailbox's Birthday episode, but Steve suddenly isn't in the puzzle. He played musical chairs, so he should've been in the puzzle.
Midori no chikyû wa makasetoke - S1-E2
Other mistake: Gai and the rest of crew are watching and old Gekigankar episode. The timer on the right corner of the tape goes from minute 49 to minute 52 between shots in the span of a few seconds (with a continuous audio in the background and dialogue between characters in the foreground). Some of the shots in the rest of the episode Miss the hour in the corner at all, and there's some back-and-forth with time (even if one can assume in that case they switched episode). (00:12:50)
Darkness and Light: Part 1 - S1-E11
Other mistake: When Gabe Jones is observing Doc Samson and Hulk emerging from the cave system in his rear view mirror, you can see his car is moving forward, but the image in the mirror remains the same size. (00:11:10)