List of episodes

Season 2: 2010-2011
Season two contains 26 half episodes and originally aired from October 2010 to mid-2011. Their titles and production codes were revealed on the Frederator Blog.

Season 3: 2011-2012
Season 3 contains 26 half episodes and originally aired on July 2011 to February 2012. Their titles and production codes were revealed on April 6, 2011 on the Frederator Blog.

Season 4: 2012
Season 4 premiered on April 2, 2012. Episode titles were posted on the Frederator Blog in March 2012.

Writing of the season had started by May 2011. According to Andy Ristaino, by February 2012, the season had been written, storyboarded and approved. The season saw the premiere of the 100th episode of the series, "The Hard Easy" (previously titled "Prince Huge"). Adam Muto reported that characters not seen since Season 1 would return, with The Earl of Lemongrab, Magic Man, the Lich, Marceline's father and NEPTR being confirmed to return. Prior to the season's airing, Adam Muto said that Marceline's backstory would be explored further, and Jeremy Shada also mentioned that Marceline and Ice King would sing together. Both took place in the episode "I Remember You." The season featured guest voices by Donald Faison, George Takei, Erik Estrada, Andy Milonakis, Emo Phillips, Bobcat Goldthwait and Susie Essman. The season featured one complete two-parter ("Return to the Nightosphere" and "Daddy's Little Monster"), however the season's introductory episode was a continuation of the season 3 finale, and the season 4 finale will continue into season 5's two-part opening episode.

Season 5: 2012-2013
In an interview with Charlie Jane Anders, Pendleton Ward revealed that the writers are currently working on season 5. Jesse Moynihan revealed that as of July 30, 2012, works on season 5 storyboards has already ended. He also stated that the pairs working on those were: Jesse Moynihan and Ako Castuera, Cole Sanchez and Rebecca Sugar, Tom Herpich and Steve Wolfhard, Skyler Page and Somvilay Xayaphone with the help of Kent Osborne. It was stated that the second Fionna and Cake episode titled "Bad Little Boy" will premiere this season. The episode will mark the return of Prince Gumball and Marshall Lee (voiced by Donald Glover). Also on tap is the "return of the possibly redeemed Flame Princess." Lady Rainicorn's and Jake's children will be born. There will also be an episode animated by David O’Reilly, an Irish animator. Season 5 will begin with the airing of a two-parter on Monday November 12, 7:30 p.m. (ET/PT) on Cartoon Network titled "Finn the Human"/"Jake the Dog." The episode titles and production codes were revealed by the Frederator blog. It was also revealed that this season was to contain a one-hour special (with the production codes 1014-125, 1014-126, 1014-127, and 1014-128), but it was pushed off for later.

Season 6: TBA
One of the show's storyboarders, Jesse Moynihan, has suggested there will be a sixth season. He later said he would be coming back to work on this season in September of 2012.

Unproduced episodes
These episodes were planned, and are known from design documents released by Frederator Studios in 2009 during the production of the first season. However, they were not produced for season one, and it is unlikely that they will actually be made into full episodes. "Brothers in Insomnia" was originally episode #692-002. However, it was scrapped, and its production number was taken by "Rainy Day Daydream," which was actually one of the last episodes produced for season one.

The Frederator blog also posted notes for an episode that was thought to be titled "You're a Beautiful Dancer". However, Adam Muto later confirmed that "You're a Beautiful Dancer" was just a quote that Finn was saying to Jake and was never meant to be an episode title. He stated that the page in question only contained random story ideas that were never fully developed into episodes.

Adam Muto has confirmed "Jakesuit" eventually worked its way into "The Silent King", which may give hints about the plot outline of "Jakesuit."