Born in Detroit in 1932, Kemal Amin “Casey” Kasem was, in the words of Frank Welker, "a rare breed, one of a kind."

To know what Casey was like in the Scooby universe, read Frank's tribute to Casey:

Here is the ending of Frank's tribute:

"Casey Kasem was a rare breed, one of a kind — a driven, creative, ethical actor, businessman and friend. He lived his dream and followed his own advice. He kept his feet on the ground and reached for the stars. And there's no doubt that he made it. Next time I look at a night sky, I'm guessing the brightest star I see glittering is my friend and funny, mystery-solving gang member, Casey. Zoinks!!!!"

From Time magazine:

"Modeled on the Maynard G. Krebs character played by Bob Denver on The Many Loves of Dobie Gillis, Kasem’s Shaggy voice was an octave higher than his own, suggesting a teen arriving late to puberty, and occasionally sullen or fretful, but always supportive of his pal Scooby.¹

Casey's importance to the Scooby universe was strongly felt when Casey quit being Shaggy in 1995.

From Business Insider:

"Shaggy's character had been known throughout the years for eating everything in sight with his trusty companion and pet, Scooby. A fact that Kasem wasn't too jazzed about. He was a hardcore vegan and an outspoken advocate for the cause.

In 1995, he was asked to portray Shaggy in a Burger King commercial. Kasem was not impressed. Refusing to promote a brand that sold hamburgers, he not only wouldn't do the commercial, but he walked out on the show entirely and a role he'd been playing for decades.

He was also not pleased that the show's creators wouldn't make the Shaggy character a vegan. In 2002, the show's producers finally came around and Kasem jumped back on board."²

Casey's radio persona collides with his "Shaggy" persona in the direct-to-DVD movie Chill Out, Scooby-Doo!

In the movie, Shaggy and Scooby find themselves in a tiny radio station on top of Mount Everest. When the station's regular DJ leaves the station, Shaggy takes over as host DJ, during which time Shaggy decides to demonstrate his radio voice. Shaggy's radio voice turns out to be Casey Kasem's regular voice.

Information Sources:

¹Corliss, R. (2014, June 15). Casey Kasem: The Voice of America. Time. Retrieved from http://time.com/2878606/casey-kasem-the-voice-of-america/

²Johnston, M. (2014, June 15). Casey Kasem Quit One Of The Most Popular Cartoons Of All Time Because Of A Burger King Commercial. Business Insider. Retrieved from http://www.businessinsider.com/casey-kasem-burger-king-commercial-2014-6