If Phineas and Ferb has taught viewers anything, it's that summer vacation from school lasts only 104 days. So we probably should have seen this coming.

After nine years and 126 episodes, series creators Dan Povenmire and Jeff "Swampy" Marsh are calling it quits on their unique blend of witty humor and eternal optimism. Summer vacation comes to an end for Phineas and Ferb next month, when the series airs its hour-long finale on June 12, 2015. "Last Day of Summer," which the episode is titled, will air simultaneously at 9:00 p.m. on both Disney XD and Disney Channel.

To mark the occasion, Disney XD is sending the Emmy Award-winning cartoon off in style by airing a 73-hour marathon of every Phineas and Ferb episode ever, beginning on June 9 and leading up to the finale. Beyond the finale, a standalone, one-hour special focusing on Agent P and Dr. Doofenshmirtz called The O.W.C.A. Files is scheduled to air this fall.

"Last Day of Summer" focuses on Candace's last chance to bust her brothers before school starts. When things go sour for her (as they always do), she sets off Dr. Doofenshmirtz' "Do-Over-Inator" to redo the day and get it right. However, using the device causes all sorts of dire consequences, like shortening the day/night cycle, ripping holes in the spacetime continuum and making her brothers vanish from existence.

As for Povenmire and Marsh, they've already signed a new deal with Disney to create and produce a brand new animated series. Entitled Mikey Murphy's Law, the show is based on the premise that "anything that can go wrong, will," while focusing on the adventures of the "fictional great-great-great-great-grandson" of Edward Murphy, for whom the law is named. The new series is expected to debut sometime in 2017.

Phineas and Ferb, a longtime ratings juggernaut for Disney XD, will continue to air indefinitely in reruns.

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