A freak accident leaves the South Park Elementary school bus teetering precariously on the edge of a cliff. As the boys relive landmark moments in their young lives, their bus driver, Ms. Crabtree, goes for help. A strange turn of events leads her to find the love of her life and her dream job as a stand-up comic.
The children are on the bus, following a diversion along a mountain pass. When the bus nearly goes over a cliff, Ms. Crabtree goes out to call for help, she tells the kids not to leave the bus, because "a big scary monster" will eat them. The kids remain there and remember past experiences.
Scenes are shown in the boys' memories from episodes such as "Cartman Gets an Anal Probe", "Weight Gain 4000", "Volcano", "Death", as well as moments from the episode itself. However, each of these memories is different from what had actually happened. For example, Stan is shown twice kissing Wendy rather than vomiting in panic when she talks to him, Kenny kills Death instead of the reverse, Scuzzlebutt's leg is played by Brent Musburger instead of Patrick Duffy, and Mr. Garrison shoots Kathie Lee Gifford because she is some kind of alien. In addition, at the end of all of them, the people in the memory eat ice cream or some variation involving ice cream. After the memory ends, whoever was recalling it says "Now that's what I call a sticky situation!" and everybody laughs, until the kids point out the actual conclusion that happened. Some of the memories are not from South Park at all; Fonzie's leap over a series of buses parodies the Happy Days episode "Fearless Fonzarelli". This is a reference to the fact that the actor who plays Fonzie, Henry Winkler, is providing the voice of the monster. Later, when one kid in a red Starfleet uniform (a reference to the name of the episode, which was originally the name of a Star Trek episode) tries to leave the bus, a gigantic black monster really does jump out. After eating him, the monster lays siege to the bus, carrying off Kenny (who presumably dies).
Ms. Crabtree, on her journey, meets a roofie-peddling Elvis impersonator named Marcus (or Mitch, as it keeps changing throughout the episode). When trying to get help, he takes her to a club where Carrot Top is performing and Ms. Crabtree insults him, appealing the audience. Marcus/Mitch then takes her to an agent; he finds her funny and she becomes a comedian. She even appears on The Tonight Show with Jay Leno. By now, she has forgotten about rescuing the stranded children. However, she then quits, but the two remain close. Back in South Park, Mr. Mackey convinces the parents that their children have run away, and they go on TV trying to get their kids to return. The kids see their parents via portable TV set in the bus and are embarrassed.
In the final flashback, Cartman recalls identifying his father, but he remembers it incorrectly with his father being John Elway (it is revealed twelve seasons later that Cartman's father was indeed a Denver Bronco, but not John Elway, in the episode "201"). When corrected by Kyle "I thought your father was your mother 'cause she had a penis.", Cartman is angered by this, and moves to the back of the bus to attack Kyle. This causes the bus to go over the cliff and break in two, and Craig to fall out into the trench. Then the bus falls into the trench, landing in a gigantic tub of ice cream. Cartman suddenly realizes how little sense everything makes and wakes up in his own bed. His mother comes in with breakfast, and Cartman explains his dream to her. She then offers him some beetles for breakfast, and they eat; she then says that beetles taste even better with ice cream. Just then, Stan wakes up in his bed, revealing to be that it was in fact his dream, then he calls Kyle to talk about the strange dream he had. Kyle claims Stan's dream is "fucked up" and offers him to go hang out with Kenny and Cartman in Happy Burger to which Stan accepts.
Meanwhile, Ms. Crabtree and Marcus/Mitch are shown sitting on a log near Stark's Pond. Ms. Crabtree says she enjoyed her time with him, but he claims that everything is a whole dream by "an 8 year old kid." However, Ms. Crabtree still wants to enjoy it a little longer.