Lady Gaga passes through Springfield via train while on her way to a concert. Seeing how low the city's self-esteem is, she takes it upon herself to cheer up the whole city. However, no one in town is more depressed than Lisa, who was voted as the most unpopular student by her peers. Lisa tries to reverse her status as one of the least popular girls in school by ghostwriting positive things about herself on the school blog under the heading "Truth Teller".
When Bart finds out her secret and reveals it to the school, her social ranking plummets to a new low until a psychic force tells Lady Gaga that Lisa needs her help immediately. After much soul searching and yelling at Lady Gaga for trying to help, Lisa realizes that her outburst helped her because she is finally expressing her anger instead of bottling it up inside her, in effect making Lady Gaga's mission successful. Lisa catches Lady Gaga just before she leaves town to apologize, and after being forgiven she and Lady Gaga perform a duet together. With Lady Gaga's assistance, Lisa and the entire town of Springfield realize that being oneself is better than being like anyone else. Just as Lady Gaga's train begins to leave again, Moe runs up to her and asks if she can help him as well, but Lady Gaga declines, stating that she's not that good. As Moe turns and walks across the train track, a second train hits him.
During the credits, Homer is heard singing his rendition of "Poker Face".