The Bus Boy is the first part of episode 12 in season 2 of Dexter's Laboratory, which aired on October 1, 1997. In this episode, Becky and Gwen take Dexter's pencil and send it to the back of the bus, where there were several legends about a boy named Billy Bloomberg who never returned. Dexter is determined to go back there.
While waiting for the bus, Dexter makes sure he's prepared for the test by pulling out his number 2 pencil out of his shirt pocket. The bus arrives and Dexter goes to sit with his friend Douglas E. Mordecai III. Mordecai shows Dexter he's ready for the test by pulling out his number 2 pencil. He and Dexter both make good remarks about Mordecai's pencil and laugh. Their laughing was interrupted as a paper airplane flies into Dexter's head and his glasses coated with spitball. Two girls, Becky and Gwen, start picking on the boy genius.
While Dexter wasn't looking, Becky mistakes his bag of textbooks as a purse, and Dexter replies in a loud and angry manner that it is a bookbag. Becky proceeds to using it as a handbag. Gwen asks Becky about the test. She replies, and Gwen takes Dexter's pencil. It then becomes a game of Keep Away as Dexter tries to reach for the pencil. The students cheer Dexter on, and the game comes to an end when Gwen throws the pencil too high and it lands in the back of the bus. Dexter is nervous at first. Mordecai convinces him to use a pen, but Dexter refuses and goes after his pencil. Dee Dee tries to convince Dexter to turn around. Dexter isn't frightened, and he continues feeling determined to go to the back of the bus.
Several students start spinning tales about Billy Bloomberg, the boy who never returned. Dexter finds all of these stories unbelievable until he sees a shadowy hand reach out from the darkness and take the pencil. He heads back there despite the concerns of onlooking students. In the back of the bus, Dexter crawls through several layers of gum and encounters a gum monster who returns his flashlight to him. Dexter sees who the real Billy Bloomberg is. Bill then goes to explain what really happened to him, and tells Dexter how he survived all of those years. Dexter frees Bill from the sticky mess using a laser pen. At the front, Dexter introduces Bill to the students, and Becky and Gwen. Dexter tells Bill that Becky and Gwen were the ones who threw the pencil toward the back of the bus. Bill responds by picking the girls up and sticking their hair in the wads of gum stuck on the ceiling. Dexter asks for his pencil, which Bill mistakes for a licorice stick. Everyone laughs as the episode ends.