On February 18, Fionna, Cake, and Neil Patrick Harris are joined by Donald Glover for another gender-switched "Fionna and Cake" take on "Adventure Time" with the special episode "Bad Little Boy."
Cartoon Network says:
Reprising his role as Prince Gumball from season three’s much-loved gender switch episode “Adventure Time with Fionna and Cake,” Neil Patrick Harris will join Donald Glover, as Marshall Lee, the musical male counterpart to fan favorite Marceline the Vampire Queen in this second installment of the Fionna and Cake (derived from Finn and Jake) saga. In this special episode, the princesses are sick and tired of Ice King’s crazy Fionna and Cake stories, so Marceline stops by the Ice Kingdom to show him how it’s done.
The fifth season of "Adventure Time" returns on Monday, February 18, 2013 on Cartoon Network.