Tommy is a student in Bart's class.
When Homer tried to help Bart get Sherri to with her to the dance, Sherri said that she'd rather go with Tommy to the dance, who Homer did understand that "he's breathtaking". Homer convinced her that Bart has inner beauty like you'd find in a rodent, and that she couldn't get anyone better (she wears braces, she dresses like a kid, and she's not getting any younger) than Bart. Which of course Mrs. Krabappel says, "He's right, grab something and don't let go." Sherri says, "Well...Bart's not so bad."