Neil voiced a character named Prince Gumball in this week’s episode of Adventure Time With Finn & Jake - Adventure Time with Fionna and Cake, following the preview that aired at this year’s San Diego Comic Con.

How I Met Your Mother star Neil Patrick Harris lends his voice to a special episode of Cartoon Network’s hit animated series Adventure Time. Neil Patrick Harris stars as Prince Gumball in Adventure Time with Fionna and Cake, a gender-swapping, parallel universe episode featuring the female “Fionna” and her cat “Cake.”

The episode premieres Monday, Sept. 5 at 8 p.m. (ET/PT). No appearance by Neil Patrick Harris would be complete with out a song.

Adventure Time introduces viewers to unlikely heroes Finn and Jake, buddies who traverse the mystical Land of Ooo and encounter its colorful inhabitants. The best of friends, our heroes always find themselves in the middle of heart-pounding escapades. Finn, a silly boy with an awesome hat and Jake, a brassy dog with a big kind heart, depend on each other through thick and thin.

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He’ll also return to Nickelodeon’s Penguins of Madagascar as Dr Blowhole this Friday, September 9 at 8pm ET/PT in Penguins of Madagascar: Blowhole Strikes Back!

Neil Patrick Harris (How I Met Your Mother) returns as the title characters’ sinister nemesis, Dr. Blowhole, in Nickelodeon’s brand-new Penguins of Madagascar special, “Blowhole Strikes Back,” premiering Friday, Sept. 9, at 8:00 p.m. (ET/PT). The hour-long special features Harris performing in four original musical numbers, two of which he is singing alongside The Penguins of Madagascar characters. The series recently garnered six Daytime Emmy Awards, including Outstanding Children’s Animated Program, Outstanding Performer in an Animated Program (Danny Jacobs) and Outstanding Writing in Animation. Year to date, The Penguins of Madagascar ranks as one of the top five animated series on all TV with kids 2-11.*

“Our viewers loved Dr. Blowhole in the first special, so we were excited to bring the character back and work with the very talented Neil Patrick Harris again,” said Brown Johnson, President, Animation, Nickelodeon. “In this second special, he has expanded his role with unforgettable vocal performances, including a stand-out power ballad.”

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Finally, Neil and Cobie talked to TVLine about season seven for Robin and Barney (beware of some spoilers) here. How I Met Your Mother returns to CBS on September 19 at 8/7c and a second brand new episode airs right after at 8.30/7.30c.