Deliberate mistake: When Alice is about to meet the queen she hides the brush covered in red paint under her dress. The brush later disappears plus Alice doesn't have any stains on her clothes.
Deliberate mistake: Rocks on the water suddenly appear when the rabbit shows up, which allow for Alice to chase him.
Chosen answer: There is no real answer. It is intended to be left unknown. See http://www.straightdope.com/classics/a5_266.html for The Straight Dope's answer.
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