Lisa is paranoid that she is getting fat. So she turns to Homer for advice, but he makes her feel worse about it. Then Grampa breaks the bad news to her, about the Simpson gene. He takes her to the attic where he shows her pictures of Bart from two years ago, he was ripped. And now he's fat. Later that night, the television confirms Grampa's explanation, citing DNA. That night Lisa is haunted by what she's learnt, and then she accepts her fate and stuffs her face with cake. Later that year we see the results of the Simpson gene, Lisa is obese.