Zoinks! One of the most successful cartoon characters in history is having a birthday. Scooby-Doo doesn’t look it but the scaredy-cat Great Dane turns 40 on Sunday. That’s 280 in dog years!

Scooby-Doo, Where Are You! is the first series to star the lovable hound and his teenage friends, Fred, Daphne, Velma, and Shaggy. Working together, the gang of Mystery, Inc. solve supernatural mysteries which typically turn out to be hoaxes. The animated pup and the “meddling kids” are played by Don Messick, Casey Kasem, Frank Welker, Nicole Jaffe, Indira Stefanianna Christopherson, and Heather North.

The series, originally based on the characters from The Many Loves of Dobie Gillis, lasted for just 25 episodes over two seasons. However, the characters proved so popular that they’ve appeared in more than 10 spin-off series, almost 20 TV and direct-to-video movies, and two feature films.

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To celebrate the gang’s 40th birthday, Cartoon Network is debuting Scooby-Doo: The Mystery Begins on Sunday, September 13th. Like the last two feature films, this TV movie features a live-action cast and a CGI version of Scooby.

The movie takes us back before the gang knew each other and for what will become their first adventure together. Coolsville High is plagued by a suspicious haunting and Fred (Robbie Amell), Velma (Hayley Kiyoko), Daphne (Kate Melton), and Shaggy (Nick Palatas) of playing a spooky prank.

Suddenly, the school athlete, the science fair-winning brainiac, the drama beauty and the school misfit must band together to clear their names. With Shaggy’s newly adopted dog Scooby-Doo coming along, the mismatched quartet discovers they have more in common than they originally thought.

For this new movie, the voice of Scooby-Doo is once again supplied by Frank Welker. He’s one of the few voice actors to play the character since Messick’s retirement and death in the mid-90’s. It’s worth nothing that Welker’s also supplied the voice of Fred in every animated incarnation of the character but one — A Pup Named Scooby-Doo.

The new movie will tell us how the groovy gang met, how they acquired their famous van, and much more. Continuity-purists will have to ignore the aforementioned Pup series, Fred’s hair color (perhaps it’s dyed), and Velma’s nationality change as well.

What can’t be ignored is the fact that the characters have been so beloved for four decades and there’s little mystery as to the reasons why.