The Magic School Bus - Season 3 Episode 4 -

Two inches tall, and trapped in a bathroom at Wanda's house, the kids have to get out before Wanda's mother (Rosalind Chao) discovers them. Gathering building materials such as spiky hair curlers, sticky Band-Aids, dental floss, and Q-tips, the kids use what they've learned about structures to construct a series of towers and bridges across the bathroom to an open window! They get across the toilet OK — but will they get past the alligator in the bathtub?