The Magic School Bus Wet All Over Ep. 18

The class is excited about going to Waterland. Wanda and Arnold are working on a project together and somehow she convinces him to go to the girls bathroom with her to get water. He accidentally leaves Ms. Frizzle s keys along with Liz in there, and worse, he forgets to turn the water off. When they leave for Waterland, Ms. Frizzle instead uses a spare key which turns her, the class, and the bus into water. (Note: This episode can be seen as a sketch of the importance of responsibility on the Kids for Character with Tom Selleck. )