TV legend Steve Allen, best known as the creator and original host of NBC's The Tonight Show, died of an apparent heart attack at the Encino, Calif. home of his son Monday night. He was 78.

"He established the format, and set the classy tone, for one of TV's great franchises," says TV Guide critic Matt Roush. "Without him, there might be no Tonight Show. And without his hilarious 'man on the street' shtick, where would Jay Leno, or even David Letterman, be?"

Letterman has long cited Allen as one of his great comic inspirations. "Steve Allen was an enormous influence on television," he says. "His early work is really the foundation for what late-night shows have become."

Johnny Carson, one of Allen's Tonight Show successors, took the news of the TV pioneer's death hard. "Steve Allen's death saddens me greatly," he says. "All of us who have hosted the Tonight Show format owe a debt of gratitude to [him]. He was a most creative innovator and brilliant entertainer."

Allen, who also headlined The Steve Allen Show from 1956 to 1961, helped launch the TV careers of a generation of renowned comics, including Don Knotts, Tom Poston, Tim Conway, the Smothers Brothers and Bill Dana.

Additionally, the entertainer — forever identified by his trademark horn-rimmed glasses — starred as the King of Swing in the 1956 film The Benny Goodman Story. He also was an accomplished musician, releasing some 40 albums and composing more than 8,500 songs. The Guinness Book of World Records called him "most prolific composer of modern times."

"Of all of TV's pioneers, there's probably no one quite as versatile as Steve Allen," Roush marvels. "He wrote, he acted, he clowned, he ad-libbed, he hosted, he guested, he wrote and sang music, he did it all. And for the longest time, TV always found room for his talents."

In recent years, Allen served as a spokesman for the Parents Television Council, a media watchdog group that worked to limit the amount of sex and violence on TV. Notes Roush: "While many of us wondered if he'd lost his sense of humor about the medium he helped establish, no one would ever have doubted the sincerity of his nostalgia for a kinder, classier era."

Allen's wife of 46 years, Jayne Meadows, described her husband as "my best friend and my partner on stage and off for more than 48 years. He was the most talented man I've ever known and the one true love of my life."

In addition to Meadows, Allen is survived by four sons, Stephen Jr., Brian, David and William Christopher, 11 grandchildren and three great-grandchildren.