The Grim Adventures of Billy & Mandy wraps up a 7-year TV run, but arriving on the finale's heels is Billy & Mandy's Big Boogey Adventure (above), the first feature-length movie based on the property. All images © Cartoon Network.

Just as the Cartoon Network series The Grim Adventures of Billy & Mandy prepares to wrap up its seven-year run, the channel is debuting the first feature-length movie based on the property. A three-hour marathon of episodes will lead up to the March 30 on-air premiere of Billy & Mandy's Big Boogey Adventure, to be followed by a DVD release from Cartoon Network and Warner Bros. Home Video a few days later, on April 3.

Billy & Mandy got its start as a never-aired short film that creator Maxwell Atoms, a former storyboard artist on Cow and Chicken and I Am Weasel, made in college. Because the Grim Reaper was a major character, "I actually never throught [Cartoon Network] would go for it," Atoms says.

But in August 2000, Grim & Evil -- which consisted of two Atoms creations, Billy & Mandy and Evil Con Carne -- won The Big Pick, an online and on-air vote-in contest held during a 53-hour Cartoon Weekend original programming marathon. Grim & Evil beat out two other contestants, Whatever Happened to Robot Jones? and Long Hair and Double Dome, by a margin of two to one. The next August, Grim & Evil became the network's 12th original series and, in June 2003, The Grim Adventures of Billy & Mandy split from Evil Con Carne and premiered as a separate half-hour series.

The feature came about when Cartoon Network was looking for some longer-format material to air and series creator Maxwell Atoms (right) pitched Big Boogey Adventure. It centers on the series' only villain, the Boogey Man.

The show's early history was somewhat rocky, according to Atoms, who reports it went on and off air a number of times before becoming established. "We had a really rough first couple of years. I'm not sure even Cartoon Network wanted it to live."

Viewers started to discover the show once it expanded to the half-hour format, and extending each storyline from seven to 11 minutes "made a big difference," Atoms says. "Seven's not really room enough to tell a story. It's just a couple of gags and that's it."

Produced at Cartoon Network Studios, Billy & Mandy tells the story of two young friends, cynical Mandy and carefree Billy and their best buddy, The Grim Reaper. The three pals deal not only with unwanted visitors from the spirit world, but with the usual challenges that face suburban kids as well. The show will wrap up after 76 half-hours and an hour-long finale that is currently being finished; over its lifetime the series has become one of the longest-running and most popular shows on the network, especially among boys.

In the two-hour Big Boogey Adventure, billed on the DVD package as "the year's best scary pirate robot comedy," Grim is stripped of his powers. To restore them, the three friends must race the Boogey Man to capture The Hand of Horror. As is true of the series, the film is full of jokes and references to horror movies and pop culture icons -- including Jason and the Argonauts and Clash of the Titans -- that have influenced Atoms. "That's what I like about animation," he says. "I can remember what I liked in my childhood and bring it back."