Spider's Little Daddy/Tricycle of Terror - S3-E1
Continuity mistake: Mandy's working on her report. The page she's on says "CORN by Mandy." A moment later, she writes the same title on another page.
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Duck/Aren't You Chupacabra to See Me? - S4-E9
Continuity mistake: Mandy is in the library working on her report. When she's working on the second page, the writing is scribble, and on top of a stack of paper. A second later, the page says "CORN by Mandy", and the stack of paper is gone.