Tommy is a fictional character in the Hey Arnold! TV Series.
He's Maria's boyfriend. Maria went on a "date" with Arnold to make Tommy jealous in "6th Grade Girls".
He also appeared with the whole city in "Arnold Betrays Iggy", once in the classroom of Mr. Frank's class in "Phoebe Skips", strangely in "The Pig War" holding Arnold's arm alongside Burt and in the "Arnold's Valentine" episode at the Chez Pierre restaurant, where he tries to get together with Ruth (though she initially mistakes him for a bus boy). He has much darker hair in this episode instead of his regular brown hair like he had in the 6th Grade Girls episode, though this is likely to simply be a continuality error. It's also possible that he and the bus boy are two different individuals who simply share the same model.