The Contest / Prove It!.The Contest: Note: This episode was the result of an actual contest where viewers could send in story ideas for an episode, and Holly Holland, who was mentioned in the episode, was the contest's winner.
Prove It!: Wanting to prove to Arthur that she is smart, D.W. hangs around with Brain, watching Nova with him, and starts her own science fair that is full of untrue facts that Arthur cannot disprove, even with Brain's help. As a last resort, Arthur brings D.W. with him and Brain to a science museum to show her how things really work, and she then reveals to Arthur that this had been her plan all along.