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.
The Grim Adventures Of Billy And Mandy (2001)
1 mistake in Spider's Little Daddy/Tricycle of Terror
Billy's Mom: Oh sorry, Billy. We weren't laughing AT you, we were laughing with you.
Billy's Dad: I was laughing AT you.