Executive producer Leonard Katzman has said over the years that his only regret was killing off April Stevens Ewing in the CBS drama “Dallas,” but he wasn’t the only one who felt that way.

By Daniel E. Slotnik April Stevens, whose rushed recording of “Deep Purple” with her brother, Nino Tempo, became a chart-topping single in 1963 and won a Grammy Award, died on April 17 at her ...