Turner Broadcasting is overhauling its toon cablers with plans to expand Adult Swim’s programming block by one hour and add advertising to Boomerang for the first time.

Adult Swim will expand into the 8 p.m. hour as of March 31. As part of the change, Cartoon Network.com will add more original digital content aimed at its core boys demographic. Boomerang, meanwhile, will be pitched to Madison Avenue as a family-friendly network designed for multi-generational fans of “Scooby Doo,” Looney Tunes shorts, “Tom and Jerry” and 1990s Cartoon Network fare such as “Dexter’s Laboratory” and “The Powerpuff Girls.”

The skedding shift for Adult Swim is a recognition that Cartoon Network’s target demo of boys in the 6-14 age range are increasingly finding their entertainment online. Adult Swim, on the other hand, is on a roll with its roster of hip and often edgy toon fare.

At the outset, Adult Swim’s 8 p.m. hour will be filled with back-to-back episodes of the long-running Fox hit “King of the Hill” and a 9 p.m. installment of “The Cleveland Show,” another acquisition from Fox. Those shows will serve as a tonal bridge to Adult Swmi’s outré originals such as “Robot Chicken,” “Rick and Morty,” “Aqua Teen” and “The Tim and Eric Awesome Show.”

“As Adult Swim continues to succeed with record ratings and connects with its audiences more than ever, it is imperative that we find a way to grow this part of the business that keeps the essence of what has made it successful and competitive,” said Stuart Snyder, Turner Broadcasting’s prexy of Animation, Young Adults and Kids Media.

Adult Swim bowed in 2001 as a twice-weekly three-hour program block splitting the channel real estate with Cartoon. It has expanded several times, most recently in 2007 to the nightly 9 p.m.-6 a.m. block that will now grow by one hour. Adult Swim routinely ranks high among the top cablers for the adults 18-34 demo, and it is particularly competitive in latenight with young men.

Cartoon Network has long had a smaller audience overall than its primary cable rivals, Disney Channel and Nickelodeon. Its biggest strength is its appeal to boys, and the digital push is an effort to keep pace with the on-demand generation.

Cartoon will heavily promote a slew of new digital content, games and apps designed for the younger set, and on-air promos will alert parents to the more adult fare coming to the 8 p.m. hour.

“We know more and more kids today are turning to digital options for entertainment content beyond their TV screen, so we’re developing a new slate of original content that will premiere on CartoonNetwork.com and our other digital platforms to feed that ever-growing appetite,” Snyder said. “Cartoon Network will always be on when and wherever our audience wants to experience it.”

Boomerang, which launched in 2000 as a showcase for Turner’s vast library of Hanna-Barbera and Warner Bros. cartoons, has finally hit the “critical mass” needed to draw advertising dollars, Snyder said.

“We’ve determined now’s the time to open the network to our partners as a new opportunity to reach family audiences, particularly parents with young children,” he said.

(Pictured: “The Cleveland Show,” “King of the Hill”)