Deliberate mistake: Gerald's little sister loses her stuffed animal, Wallie. The window it's sitting by is obviously a closed window. Somehow, Arnold is able to look out of it, even though there is a pane of glass there.
The High Life / Best Friends - S2-E10
Deliberate mistake: In "The High Life", there is a scene where Stinky submerges his head in a tank of water. He delivers the line, "Gee willickers, it's still ticking", and everyone somehow understands what he is saying with his head underwater.
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Suggested correction: Nobody responds to what Stinky says, so there's no reason to assume that everyone understood him.
