The Lab Brat

“The Lab Brat” was the seventh episode of the first season of Daria.

Plot
Behavioral conditioning via positive or negative reinforcement is the lesson in Daria's science class, with Ms. Barch lapsing into man-hating diatribes whenever she thinks of her ex-husband (who left her for a younger woman). After Daria provides a particularly colorful example of the topic, Ms. Barch pairs up the students for experiments involving the conditioning of a mouse. Kevin and Brittany naturally expect to wind up as partners, but it is not to be: Daria gets partnered with Kevin, while Brittany winds up with the lecherous Upchuck. Upon hearing this news -- and Helen's admonishment to Daria that this opportunity could propel her up a few rungs on the school's social ladder -- Quinn schemes to nab Kevin for herself. When Kevin arrives, Quinn turns her flirt circuits to full power, but Daria puts her plan into motion by distracting him with the Pigskin Channel. Getting Kevin out of her hair, and safely male-bonding with Jake, leaves Daria free to work on the project without interference from the scatter-brained Q.B. Meanwhile, Brittany arrives at Upchuck's house in full disguise, wanting nothing more than to get the project over with as quickly as possible. Upchuck, however, has other plans, which he swiftly puts into motion. He reveals that he has photographic proof of Brittany's dalliance with Sam Stack, quarterback of the Oakwood football team, which quickly turns the horrified cheerleader into Upchuck's personal servant. Humiliated, angry, and insanely jealous, Brittany schemes to sabotage what she thinks is Daria and Quinn's attempts to steal Kevin away from her. She does this by stealing Daria's mouse and giving it to her sadistic little brother, Brian, who proceeds to torture the poor creature. When Daria finds out, she backs Brittany into a corner by telling her that without the mouse, Daria and Kevin will have to work on a make-up project... which would mean Kevin spending even more time away from Brittany. The two girls make a deal: Brittany hands over the mouse, and Daria hands over Kevin (who she never wanted in the first place). Unfortunately, Daria discovers that Brian has ruined the mouse's conditioning; all it does now is hide in a corner of the maze and quivver with fear. Unable to train a new mouse in time, Daria makes the best of the situation by angling her presentation at Ms. Barch's hatred of men. This earns Daria an "A", and the lazy Kevin a "D" (which he naturally celebrates). Brittany and Upchuck, however, each earn an "F" for their lame project (consisting of a maze, and a tube running straight from the starting point to the cheese). After class, Kevin informs Daria that he's having a party, and decides to ask her... to ask Quinn if she would attend.