Charlene's Flat World - S3.E9

When Charlene's class is assigned to think of an original idea, her world-is-round theory falls flat, and she's tried for heresy. She get's arrested stating that the world is round and everybody believes that the world is flat. So she decides to prove them wrong by traveling with Robbie to the end of the earth to there sudden death. But they return and everyone realized now the world was round.