"In the Arctic" is the second episode of season three and the twenty-eighth episode overall of the animated children's series The Magic School Bus. It originally aired on September 21st, 1996.
Arnold wants to know what happened to the heat from his hot cocoa. Ms. Frizzle thinks it is fitting to learn about heat in the land of ice and cold, so she takes the class to the Arctic. However, she accidentally drives the bus into the water, and the engine freezes. To make matters worse, it has been trapped on an ice flow with Phoebe, Ralphie, and Liz. The rest of the class will have to get to it and heat it up to escape.
During a fall morning in class, the class is having lunch at the cafeteria, and Arnold likes the cold because he gets to have hot cocoa. He holds up a cup to get served the hot cocoa and finds that Ms. Frizzle is on cafeteria duty. She serves Arnold the cocoa with two marshmallows. Arnold joins the rest of the class at a table, only to learn that another student named Harry Arm has taken his spot. So Arnold is relegated to a table next to an open window and takes a sip of the hot cocoa, only to learn that the drink is cold. When he asks "Where did all the hot go", he inadvertently gives Ms. Frizzle an idea.
The teacher has taken the class on a field trip to Antarctica and offers them jackets as well. While Ms. Frizzle searches for optimum jackets, the bus ends up driving into water, and the bus' engine eventually freezes, causing the bus to come to a complete stop. Dorothy Ann then reads in her book that the Arctic's temperature can drop down from 100 degrees to 0. Since Liz is cold-blooded, the cold has a soporific effect of her body, and she ends up dropping down to the ground in stupor. So Phoebe keeps her warm inside her jacket. Wanda also finds a trunk under the seat and Ralphie opens it to find what appears to be ski goggles inside, only for Ms. Frizzle to state that they are "heat peepers. The class put them on to find red lines hovering around Ms. Frizzle's body. Carlos surmises that moving heat means losing heat. The class then discover that the heat is going out of the bus. Arnold then learns that his hot cocoa became cold because the heat went out of the top and through the metal mug since the window was opened and let all the cold air inside the cafeteria for the heat to escape. Arnold then comes across wood and makes a fire outside with them. Ms. Frizzle makes lemon water tea with the fire and Ralphie decides to break the wood to use it for firewood. He runs inside the bus and breaks a huge wood block that had hot water bottles inside. Ms. Frizzle pours the tea inside the hot water bottle and the class discover how much heat is going inside the hot water bottle. Carlos stuffs the hot water bottle inside his jacket and Arnold decides to put the hot water bottles onto the bus engine to keep it warm so that it would run again. The plan doesn't have a chance to be implemented, however, when the icy ground cracks and the bus goes along with the ice flow, with Ralphie, Phoebe, and Liz going along with it.
The class chase after the bus and Carlos drops his hot water bottle. He picks it up to find that the heat has now escaped out of the bottle. Arnold borrows D.A.'s book and tears out a page of it to put inside his jacket. The other class follow suit and Phoebe and Ralphie watch as the paper the class is stuffing inside their jackets makes them warmer. Liz gives the two a repair manual and Phoebe tears out a page to stuff in her jacket. The class then find some source of heat and run to it to get warm, only to find that the heat is really the breath of a polar bear. Ms. Frizzle comes right in time to shrink the class as they end up into the polar bear's fur (which they later discover. Inside, they find that it is warm and that a polar bear's fur has the same effect on their body temperature as the papers they stuff in their jackets. Ms. Frizzle tickles the bear's skin, causing it to scratch the class off it. Meanwhile, Ralphie and Phoebe are looking for the rest of the class and discovers that the ice flow the bus is on is breaking apart, much to the rest of the class' horror.
The bus continues to float through the water and Phoebe looks at the page inside her jacket to discover that there are blankets inside an overhead cabinet, only to come across a fat substance called blubber which traps heat. Just then, a walrus climbs on to of the ice flow and Ralphie and Phoebe learn that the walrus' skin is made out of blubber to keep the heat inside of them. So they use the blubber to keep warm and exit the bus to inform the class how to keep the heat. Liz activates the horn to spray the blubber onto the rest of the class. They hop inside the cold water and swim to the bus, but not before Wanda was hesitant to go in the water before being told by Keesha, Tim, and Arnold that the blubber keeps them from getting cold and when Wanda jumps in, she realizes that she felt warm in the water due the blubber.
Arnold then comes up with an idea to trap the heat he and the class are making so the heat can't escape. But he never contrived how to do it. But when Liz comes across a secret stash of igloo-building equipment, Arnold decides that the class should build an igloo around the bus with snow since, despite its low temperature, its light and fluffy and has tiny air pockets to trap the heat. The bus eventually warms up and Ms. Frizzle transforms the bus into a helicopter to fly away.
Back inside the school cafeteria, Ms. Frizzle serves Arnold a hot cocoa, which Arnold stuffs inside a quilted cocoa cozer to hot in the heat. Arnold comes across the table with the rest of the class and Harry is impressed of Arnold's innovative creation to keep the cup of hot cocoa warm since he was in Ms. Frizzle's class last year. He offers Arnold a seat with him and the rest of the class and they drink their hot cocoa together.
Dorothy Ann: According to my research, you won't last more than three minutes in water this cold!
- The voice actor for Harry Arm, the boy who took Arnold's seat in the cafeteria, is Amos Crawley, the original actor of Arnold, who was later replaced by Danny Tamberelli in the second season onwards due to Amos going through puberty. That's why Danny Tamberelli is actually American whereas Amos Crawley is Canadian. After Arnold starts explaining about heat, Harry finishes the process and says, "I was in Ms. Frizzle's class last year." Harry makes a second appearance in "Works Out."
- Carlos does not say any puns in this episode.