Question: Jason Ritter and Kristen Schaal voice over characters in the episode "Weirdmageddon 3: Take Back The Falls" of Gravity Falls which is made for what children's channel?

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Dipper Pines: Mason "Dipper" Pines is a fictional character and one of the main characters of the Disney XD animated series "Gravity Falls".  The character is voiced by Jason Ritter, and designed by and loosely based on the childhood of series creator, Alex Hirsch.  The character first appeared on the unreleased, unnamed pilot created by Hirsch with which he pitched the show; he later appeared on the first episode "Tourist Trapped".  Dipper, along with his twin sister Mabel Pines, stars in every episode of the show.  Dipper is the star of the Gravity Falls series of shorts titled "Dipper's Guide to the Unexplained" and also appears in the shorts "Fixin' it with Soos" and "Mabel's Guide to Life".

Sally (Flight of the Conchords): "Sally" is the pilot episode of the American television sitcom "Flight of the Conchords".  It first aired on HBO on June 17, 2007.  In this episode, New Zealanders Jemaine Clement and Bret McKenzie of the band Flight of the Conchords have moved to New York City to try to make it in the United States.  At a party, Jemaine falls for, and subsequently begins dating, Sally—Bret's former girlfriend.  As Jemaine's attentions focus on Sally, a lonely Bret is forced to deal with the advances of Mel (Kristen Schaal), the band's obsessed—and only—fan.  Meanwhile, Murray (Rhys Darby), the band's manager, helps the band film their first music video, although they cannot afford decent costumes or proper video equipment.

Jason Ritter: Jason Morgan Ritter (born February 17, 1980) is an American actor, and the son of actress Nancy Morgan and actor John Ritter, known for his roles as Kevin Girardi in the television series "Joan of Arcadia", Ethan Haas in "The Class", as Sean Walker in the NBC series "The Event", and as the voice of Dipper Pines in "Gravity Falls".  He also played the recurring role of Mark Cyr in the NBC television series "Parenthood", for which he received an Emmy Award nomination.

Not What He Seems: "Not What He Seems" is the eleventh episode of the second season of the American animated television series "Gravity Falls", created by Alex Hirsch.  The episode was written by Shion Takeuchi, Josh Weinstein, Jeff Rowe, Matt Chapman, and Hirsch, and directed by Stephen Sandoval.  The series follows twelve-year-old twins Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who stay for the summer with their grand uncle Grunkle Stan (voiced by Hirsch) in a tourist trap called the Mystery Shack, set within the fictional town of Gravity Falls, Oregon.  In this episode, Dipper and Mabel begin to question who Stan really is after officers arrest him for stealing chemical waste.  The episode, which breaks the show's status quo by revealing Stan's brother, ends with a cliffhanger to the second half of the season.

Kristen Schaal: Kristen Joy Schaal ( ; born January 24, 1978) is an American comedian, actress, voice artist and writer.  She is known for her roles of Mel on the HBO series "Flight of the Conchords", The Heart, She Holler as over-sexed Hurshe, Louise Belcher on FOX animated comedy "Bob's Burgers", and Mabel Pines on "Gravity Falls".  Other roles include her appearances as a commentator on "The Daily Show", Amanda Simmons on "The Hotwives of Orlando", Hazel Wassername on "30 Rock", Victoria Best on "WordGirl", Trixie from the "Toy Story" franchise, Anne on "Wilfred" and she has appeared on Celebrity Family Feud.  Since 2015, she has co-starred alongside Will Forte in the Fox comedy "The Last Man on Earth", playing the role of Carol.  She was nominated for a Primetime Emmy for her role of Sarah Lynn in "BoJack Horseman".

List of Gravity Falls episodes: "Gravity Falls" is an American animated series created by Alex Hirsch for Disney Channel, and now for Disney XD.  The series revolves around the various antics of two fraternal twins, Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who were handed over to their Great Uncle (or "Grunkle") Stan (voiced by Alex Hirsch), who runs a tourist trap called The Mystery Shack, in the town of Gravity Falls, Oregon.  They soon realize that the mysterious town holds plenty of secrets.  When Dipper obtains an old journal that he finds in the forest, they find that their everyday lifestyle changes with odd things and creatures they encounter.

Mabel Pines: Mabel Pines is one of the lead characters of the Disney XD (formerly Disney Channel) animated series "Gravity Falls".  The character is voiced by Kristen Schaal, and designed by the series creator, Alex Hirsch.  She is inspired by Hirsch's own twin sister, Ariel Hirsch.  Mabel first appeared on the unreleased, unnamed pilot created by Hirsch which he used to pitch the show; she then appeared on the first episode "Tourist Trapped".  Mabel, with her brother Dipper Pines, stars in every episode of the show.  Mabel also has two series of shorts dedicated to her: "Mabel's Guide to Life" and "Mabel's Scrapbook".

Gravity Falls: Legend of the Gnome Gemulets: Gravity Falls: Legend of the Gnome Gemulets is a platform video game for the Nintendo 3DS, developed and published by Ubisoft and produced by Disney Interactive Studios based on the animated Disney series, "Gravity Falls".  The game utilizes UbiArt Framework engine, and was released on October 20, 2015.

Gravity Falls: Gravity Falls is an American animated television series produced by Disney Television Animation originally for Disney Channel (and then later for Disney XD) from June 15, 2012 to February 15, 2016.

Weirdmageddon 3: Take Back The Falls: "Weirdmageddon 3: Take Back The Falls" is the series finale of the American animated television series "Gravity Falls", created by Alex Hirsch.  The episode was written by Shion Takeuchi, Mark Rizzo, Josh Weinstein, Jeff Rowe, and Hirsch, and directed by Stephen Sandoval.  The series follows twelve-year-old twins Dipper (voiced by Jason Ritter) and Mabel Pines (voiced by Kristen Schaal), who stay for the summer with their grand uncle Grunkle Stan (voiced by Hirsch) in a tourist trap called the Mystery Shack, set within the fictional town of Gravity Falls, Oregon.  In this episode, Ford (voiced by J.K. Simmons) discovers the extent of Bill Cipher's plans, while the Mystery Shack crew forms a plan to fight back and reclaim the town.  A final confrontation with Bill leads to the Pines family's ultimate fate and greatest sacrifice.

Supporting paragraphs: Weirdmageddon 3: Take Back The Falls Gravity Falls
Answer: Disney Channel