"Gets Ready, Set, Dough" is the ninth episode of season one of the animated children's series The Magic School Bus. It originally aired on November 5th, 1994.
It's Ms. Frizzle's birthday, and a field trip to the bakery seems perfect, until the bus' shrinkerscope malfunctions. Carlos convinces Ms. Frizzle to continue the trip so she can go to the auto parts shop next door to the bakery. On the way there, the bus shrinks everyone, but Ms. Frizzle continues on to the auto parts shop, leaving the class to learn about baking. They experience chemistry first hand as they try to make a cake when they are tiny, and things get crazy when the bus ends up getting baked inside the cake.
Ms. Frizzle is fixing the bus and the bus capriciously malfunctions. Inside the classroom, the students rehearse for a surprise party to throw Ms. Frizzle for her birthday. When Arnold feels that something is missing, Dorothy Ann remembers her chemistry experiment and mixes water, sand, and cement to "get something new", which is cement. The class then realizes that they forgot the cake and cancels the surprise. A gloomy Ms. Frizzle walks into the classroom and informs the class that the field trip is cancel due to the bus' malfunctions. The field trip was going to be a bakery to learn about chemistry and Carlos decides to convince Ms. Frizzle to continue the trip, prompting Ms. Frizzle to schedule the field trip regardless of the bus issues.
As the bus rides through the city streets, it shrinks down to size. But Ms. Frizzle doesn't let that stop the field trip. She accelerates the bus through the door slot inside the bakery, which an Italian chef is working inside of. The bus sprouts wings and fly over the baked goods. Carlos suggests that the class should make their own cake, but they have to do it while inconspicuous from Ms. Frizzle's eye, for they want it to be a surprise for her. So Carlos convinces Ms. Frizzle to go to the auto parts shop next door to the bakery and the teacher puts Liz in charge before leaving.
Liz rides the bus and flies into the kitchen, where the chef catches it and mistakes it for a moth. He swats at it with a fly swatter and the bus disappears behind a couple of jars before transforming into a normal mini-sized bus. As the chef leaves, the students read the cookbook for the cake recipe. Carlos orders Ralphie to get 2 eggs, Tim and Wanda a cup of sugar and flour, Liz a teaspoon of salt and cream of tarter, Keesha milk, Phoebe butter, Arnold baking soda, and Dorothy Ann the mixer. The students get to work and Carlos runs off to get the chocolate.
The students grab all the ingredients for the cake and Ms. Frizzle returns to see how the students are doing on their work. Dorothy Ann, who learned that baking soda mixed with water makes vinegar, distracts Ms. Frizzle and asks for her help with an experiment. While the other students work on making the cake, the bus once again shrinks down to size in an arbitrary manner, shrinking the class even smaller than they were before.
Carlos leaves after telling the class he has another idea. While Carlos is away, the class find cubes of salt and diamonds of sugar. They learn that mineral look much different when looked at in a much smaller perspective. Meanwhile, Carlos has used the spoon as a catapult and flings salt into the bowl. The class enter the bus and add the other ingredients inside the cup. They eventually learn that flour, when viewed close up, is made of different parts as well. When they mix into the chocolate, they learn how the colors change and that they could still see which of the bits are chocolate. Little do they know, the chef is watching and is convinced that the bus is a bug flying inside the kitchen. So he contacts the Smug Bug Pest Control via telephone.
As the bus continues to add in the ingredients, it unwillingly flies to Ms. Frizzle, who is still focused on Dorothy Ann's experiment. So Dorothy Ann distracts Ms. Frizzle again and shows her what happens when a bunch of baking soda with a sparse amount of water inside, which causes the baking soda to overflow inside the bottle. So Dorothy Ann adds a balloon to the bottle and Ms. Frizzle tells her that baking soda and vinegar makes a gas that pushes out the balloon, which is tantamount to filling a tire with air. Ms. Frizzle then concludes that the bus needs new tires and goes to the auto parts shop to find out the price of new tires.
Meanwhile, it is revealed that the Smug Bug Pest Control thinks that the chef is crazy, prompting the chef to do the work himself. While the bus mixes all the ingredients together inside the bowl, the class learns that air is getting beat into the mixture and all the ingredients coalesce to create one new thing, which is cake batter.
The students then learn that cooks and chemists are alike: both measure out ingredients and mix them together to make something new, the only difference being the cook gets to taste his/hers. When the chef reappears into the kitchen, the bus drops into the cake batter. The chef notices the bowl of batter and pours it into a cake pan. He stores it into the oven and turns it on, baking the cake, much to the students' horror as they are getting baked along with it.
While the students are getting baked inside the cake better, they notice a person dressed in white approaching the bus. The person dressed in white enters the bus and turns out to be Ms. Frizzle, who reminds Liz of the heat shield. So Liz turns on the shield and the class feels much relieved. Dorothy Ann explains that the baking soda is making bubbles around the batter. When they hear a steaming sound, Ms. Frizzle explains that the water in the batter is vaporizing, thus expanding the bubbles and making them warmer. Just then, the batter solidifies, and the students learn that the cake is done. A pessimistic Arnold fears that the students will get eaten along with the cake. Ms. Frizzle pushes a button on the bus, which quickly breaks down. Dorothy Ann has a solution and decides to use baking soda and vinegar to create the gas pressure to push the bus out of the cake.
So just as the chef finally takes the cake out of the oven, the students use the vinegar mixture to propel the bus out of the cake and back to the classroom, where the students finally throw Ms. Frizzle the surprise party and offer her a cake the baker at the bakery gave them. Arnold cuts Ms. Frizzle a slice with a hole shaped as a bus, and Ms. Frizzle states that "chemistry is a piece of cake", evoking laughter from the other students.
- The TV tie-in book was called "Gets Baked in a Cake."
- Veteran film and television comedian Dom DeLuise provided the voice of the baker.
- This is the first episode to involve the guest character in the closing review spot, and also the first of a few times a child who saw the show appeared in person.