"Ah! Leah!" was Donnie Iris' (given name: Dominic Ierac) first solo hit, but he had an interesting career before that. He started as the lead singer of The Jaggerz, who had a huge hit in 1970 with "The Rapper." After The Jaggerz broke up, Iris was asked to join Wild Cherry, who were popular based on their 1976 hit "Play That Funky Music." And after Wild Cherry broke up, Iris went out on his own with Mark Avsec, the keyboard player for Wild Cherry.
Iris' first album, 1980's Back on the Streets, went to #57 on the charts, while "Ah! Leah!" hit #29. Iris would go on to have 5 more charting singles, including two more top 40 hits through 1985, so there is no one hit wonder story here. However, legal problems with his record label prevented any new material from being released from 1985 through 1992, which effectively ended Iris' mainstream popularity. Even so, Iris (and Avsec) continue to record and perform to the present day.
Cool trivia fact: The actress in the "Ah! Leah!" video is rumored to be Joanna Lumley, who became famous as Patsy Stone in the BBC comedy Absolutely Fabulous.