S21E15 · Stealing First Base (2010)

Principal Skinner announces that Mrs. Krabappel was called out of town and budget cuts dictate that, until she returns, the school's two fourth grade classes will merge. Bart reluctantly shares a desk with Nikki and develops a flirtatious rapport. Bart talks to Grampa about his new crush, and at Grampa's suggestion, gives Nikki a kiss. But when Nikki starts sending Bart mixed signals, he swears off women forever. Meanwhile, Lisa's classmates ostracize her for being an overachiever, and First Lady Michelle Obama, a self-professed nerd, comes to Lisa's defence.