"Ups and Downs" is the thirteenth and final episode of season two and the twenty-sixth episode overall of the animated children's series The Magic School Bus. It originally aired on December 2nd, 1995.
During breakfast, Wanda watches the news of talk show reporter Gerri Poveri reporting that there is a sea monster in Walker Lake (apparently based on the Loch Ness Monster, as it is also plesiosaur-like). Wanda's mother, however, scoffs at this and tells Wanda that Gerri Poveri is only making this up.
Wanda rides to Walker Lake, only to find that the class beat her to it already. Phoebe uses a banana as a bait, only for it to float. Carlos jokingly states that he likes banana splits better. Tim decides to use his monster camera (wrapped in a plastic block) to send it to get a better view of the monster, only to find that it floats too. Wanda arrives just in time to dress in her swimsuit (dressed under her clothing) prepared to catch the Loch Ness Monster. Ms. Frizzle then arrives, despite the fact that it is the weekend, and Wanda explains to her about the picture of the Loch Ness Monster the talk show reporter on television showed on television. But Dorothy Ann reminds her that pictures can be fake. Gerri Poveri arrives via helicopter and warns the others to stay out of the water. The others, however, don't heed the talk show reporter, for they are very eager (especially Wanda) to find it, and Wanda notes that Gerri doesn't own the lake. So the bus arrives and Liz transforms the bus into a submarine.
Everyone enters the submarine bus. However, the bus' automatic sinker lever is rusted. Liz forgot to swab the deck and dry the sinker linker the last time the bus went underwater. They will have to find some other way to get it to sink. Using Phoebe's juxtaposition of a floating banana and a sinking rock, the class succeed by adding weight and "crumpling" the bus. Liz steers the submarine bus as the class navigates through the underwater lake, oblivious that Poveri is also there in her underwater boat. She uses it to untie the weights supplemented to the submarine, causing the submarine bus to resurface.
Once on top of the surface of the water, Ms. Frizzle tells the class that the water pushing the submarine bus is what causes it to float. So Tim decides to supplement rocks inside the plastic box to sink his camera underwater. Phoebe tries to feed the Loch Ness Monster a peanut butter sandwich, only for one half of the bread to float on top of the water. Phoebe then crumbles the other slice of bread to a small ball and tosses it into the water, only to discover that it sinks as opposed to the bread slice. Ms. Frizzle explains that it is the size of the breads that differ: the big, flat slice floats while the small, balled-up one sinks.
So the class enter the bus and Liz activates the crumple buttons, causing the bus to crumple and sink. The class learns that the more the bus crumple, the less water it shoves out of the way, and the less the water pushes back on it. As the bus finally hits the bottom of the lake, Wanda exits the bus, which begins to float up again. Wanda ends up getting up ankle caught to an underwater seaweed, and the bus can't get any smaller due to the crumple buttons being jammed. Carlos exits the bus and pulls the plugs of the bus to release some of the water inside, causing it to sink again. Wanda, meanwhile, finally comes across what appears to be a Loch Ness Monster
As Wanda struggles to extricate herself from the seaweed, she inadvertently punches the monster and discovers that she has punched off its nose. Wanda then realizes that it was only fake and that Poveri made up the story to increase her ratings. Wanda rebukes the talk show reporter or her duplicity, which Poveri calls "creative journalism". Wanda swims to the bus and informs the rest of the class of the truth. Arnold suggests that the class should use air to push the water out to make the bus float again since air is lighter than water. So the class pumps air into the bus to pump the water out and the bus begins to rise on top of the surface again. Unfortunately for them, Poveri uses one of her gadgets of her underwater boat to pull one of the plugs of the bus to cause it to sink again, and Poveri returns on surface to record the news.
Back underwater, the class view the fake monster about to float on top of the surface of the water, giving Phoebe an idea to un-crumple the us to expand in size. This plan works, and Wanda and Tim use Tim's camera to get a footage of the fake monster. Wanda released the the fake monster from the rope which causes it float and burst out of the lake right underneath Poveri's helicopter knocking her into the water and Wanda unplugs the fake monster, causing it to deflate as Tim gets a footage of it.
At Poveri's talk show, the class are seen with the talk show reporter, who apologizes to the viewers for her duplicity as the footage of the truth is being shown on camera. Ms. Frizzle concludes that "the truth always floats to the surface" (as Gerri herself said).
- Arnold does not say "I knew I shoud've stayed home today" in this episode.
- This is one of the episodes that Arnold wasn't nervous about the field trip.
- Wanda's last name is revealed to be Li.