"In the City" is the twelfth episode of season four and the fifty-first episode overall of the animated children's series The Magic School Bus. It originally aired on November 29th, 1997.
The class goes on a "normal" field trip to the zoo and learn about animals in the city. Tim states that foxes won't live in the city on their own if not for the zoo, and Dorothy Ann reads in her book that peregrine falcons are cliff dwellers who catch and eat other birds. When the zoo begins to close, the rest of the class searches for Ralphie and Wanda, who are watching opossums hanging from a tree branch by tails. Things don't stay normal for long when Ms. Frizzle comes around via bus and the students enter the bus inside. When they explain to Ms. Frizzle that it is not feasible for zoo animals to live in urban habitat, Ms. Frizzle changes them all in to city animals (Tim, Arnold, and Phoebe are foxes; Ralphie, Wanda, and Keesha are possums; Dorothy Ann and Carlos are falcons, and Ms. Frizzle is a raccoon). They hide from the passersby and attempt to enter the bus. But when the bus, which turned into a bear, wanders off, the class attempts to go after it. Carlos and D.A. fly after it and the bus is on its way downtown. Carlos and D.A. inform the rets of the class this and they split up on a search for the bus. Phoebe, Tim, and Arnold notices an opossum crossing the road without looking the slightest bit worried and eats an apple core from the garbage. Just then, a dog breaks free from his leash and chases after the fox-transformed students.
The children hide inside a shed and the dog's owner finally catches him and takes him with him. Just then, a plant pot spills and a raccoon emerges from behind it, much to the students' confusion. The raccoon devours the worms from the soil and the students exit the shed to meet the rest of the class outside. D.A. and Carlos then fly away to search for the bus and find night hawks flying below devouring moths. Carlos attempts to eat one of them. But D.A. stops him and the two continue searching through the city. They rest on top of a skyscraper and D.A. quotes Ms. Frizzle's line, "One person's skyscraper is another falcon's cliff".
Meanwhile, Arnold runs through the city to search for food and the rest of the class follows suit. They end up in the alley and some humans spot the bus which appears to be a bear in the alley. While they attempt to call someone, the rest of the class approaches the bus and spots rats, who are scared away by an opossum. The opossum eats from the trash bag and the class eats out of the garbage themselves. Arnold finally concedes that maybe some wild animals can survive in the city and Phoebe and Tim continue to search for the bear-transformed bus.
Things escalate when animal control is looking for it. If the class doesn't get to it in time, they'll remain city animals forever. Meanwhile, D.A. and Carlos search for the bus themselves while flying above the city and the rest of the class navigate through the train tracks. They spot a fox scampering up the hill and the class follows it. They find that the fox has a spouse and babies, who they feed dead animals to, inside a local graveyard and hide just in time to spot the zookeepers searching for the bus transformed into a bear at an attempt to tranquilize it and take it to the woods.
So the class searches for the bus and reports the bad news to D.A. and Carlos when they arrive. Phoebe begins to panic since a bear can't survive the city streets and the class takes a whiff of food. They enter a local dump and finally find the bus into a pile of junk. The zookeepers search for the "bear" through the junk yard and Ms. Frizzle scares the zookeepers away. They wake up the bus and congratulate it. Liz transforms the bus and the others back to normal and the class explains how the wild animals can survive in the city by finding food, shelter, and safety, and they are very adept of staying clandestine from the humans' view. They enter the bus and Ralphie concludes that, "This has been a bear of a field trip" right before the bus drives away.
Transformations the Bus Used