Jack E. Leonard, 62, night­club and TV comic who made the abrasive, one-line gag into an art form, died of complications following heart surgery in Manhattan. A onetime lifeguard, Leonard began competing in Charleston contests during the '20s, then graduated to the big-band circuit as a comedian. Portraying the angry, fast-talking fat man (his weight yo-yoed between 200 and 330 lbs.), he eventually became a frequent TV guest whose comedy format never varied — a skeleton routine augmented by ad-lib insults to audience and fellow performers alike. "I could be funny for hours on your show," he once told a rival comic, "but I wouldn't want to change the format."