Mortal Folly and Mortal Recoil

"Mortal Folly" introduced The Lich—the series' primary antagonist—who is voiced by Ron Perlman

Both "Mortal Folly" and "Mortal Recoil" were directed by Larry Leichliter, with Pat McHale and Sanchez serving as creative co-directors and Nick Jennings serving as art director. "Mortal Folly" was storyboarded by Rebecca Sugar and Adam Muto, whereas "Mortal Recoil" was storyboarded by Jesse Moynihan and Cole Sanchez. Both were episodes based on a story by Mark Banker, Kent Osborne, Patrick McHale, and series creator Pendleton Ward.[2][3]

"Mortal Folly" and "Mortal Recoil" feature the first substantial appearance of the Lich, the series' primary antagonist, who made an early appearance in the season one episode "His Hero" being defeated by Billy in a flashback. The Lich had appeared in concept drawings in the series' pitch bible, which Ward himself had created in 2007.[4] Ward's original drawing was re-designed by former creative director McHale; he purposely gave the Lich a desiccated and dried-up look, and was instrumental in crafting the Lich's rotting appearance.[5][6] In both this episode and other episodes where the character appears, the Lich was voiced by Ron Perlman.[7] In the original outline for "Mortal Folly", the Lich had several lines that played him off as a stereotypical villain. Sugar and Muto decided to make him into a more "scary and dangerous" character, and purposely played up the darker elements of the episode.[5] The scene featuring Finn stuffing the sweater into the Lich's eye sockets and then ripping his skull apart was inspired by an artistic design idea Sugar had had when she was in high school; she had wanted to draw a comic featuring a small person getting into a fight and being pushed up to the ceiling.[5]

In the initial storyboard, the Lich's lair was not specifically designed to be a subway. This was added later by the background designers.[5] The undead skeletons that attack Finn and Jake were originally supposed to be "specific undead from [Dungeons & Dragons]".[8] However, Ward changed his mind and tasked Andy Ristaino, a character designer for the series, with stylizing the corpses. Ristaino designed them to resemble "east coast commuters [all] bundled up for winter."[8] He strove to make them look like people you might see on a subway, such as a bike messenger, a couple, man in a "goofy hat", and a man wearing a suit.[8] Originally, when the Lich set off his bomb, the storyboard featured a simple mushroom cloud. Ian Jones-Quartey, one of the series' storyboard revisionists, however, added a face to the blast. Ristaino then added skulls to the smoke.[9] The series' staff liked this version so much that they later included it on the title card.[9][10]

The snail, an easter egg that appears in every episode, appears in the episodes and plays a prominent part. Originally, the snail was inspired by the in-jokes in episodes of The Simpsons, and was Ward's attempt to "make a game out of every episode of Adventure Time, where you could freeze-frame and find things in the background", such as the snail.[11] However, in "Mortal Folly", the snail serves as the catalyst for the Lich's escape. The snail would also play an important part in other mythology-heavy episodes like "In Your Footsteps", and "The Lich". Osborne later noted that the snail's appearance was pleasing to fans who knew that the snail had been appearing in all the episodes and had actively searched for it before.

Because a large amount of the action in "Mortal Recoil" takes place in Bubblegum's bedroom, Moynihan was worried that the scenes would not carry interest and "people would get bored".[12] As such, Moynihan and Sanchez created the scenes "trying to be simultaneously funny and terrifying".[12] Ward noted that he liked to be "laughing and freaked out", and that the scenes work in this manner.[10] Former storyboard artist Adam Muto commented that the possession scenes turned out "nice and off-putting".[13] Jones-Quartey called the shot of a possessed Princess Bubblegum melting "terrifying".[9] Although the series tries to avoid "cartoon physics",[14] Sanchez and Moynihan were forced to work around this during the scene when Bubblegum throws Finn and Jake through a wall without harming them. Moynihan later rationalized that the wall was made of candy, and thus was harmless.[12]

The end of "Mortal Recoil" introduced the plot thread of Bubblegum de-aging to a 13-year-old girl. This would be expanded upon and eventually resolved in the third season episode "Too Young".[15] The younger version of Bubblegum was voiced by Isabella Acres, who would reprise her role in "Too Young".[15][16] According to Moynihan, there were initially "rumors" to keep Bubblegum young for several episodes, but the character eventually reverted to normal after only two episodes.[17]

"Mortal Folly" and "Mortal Recoil" first aired on Cartoon Network on May 2, 2011. Both episodes were viewed by 1.92 million viewers and scored a Nielsen rating of 1.3/2 percent. This means it was seen by 1.3 percent of all households and 2 percent of all households watching television at the time of the episode's airing.[18] The episodes first saw physical release as part of the 2012 Adventure Time: Jake vs. Me-Mow DVD, which included 16 episodes from the series' first three seasons.[19] It was later re-released as part of the complete second season DVD in June 2013.[20] The season was originally supposed to end with "Mortal Folly"/"Mortal Recoil", but due to a scheduling conflict, "Heat Signature" was the last episode of the second season aired.[21] Despite this, Ward still considers the two-parter to be the real season finale,[22] and the two entries are the last episodes featured on the second season DVD release.[20][23]

Tyler Foster of DVD Talk praised both "Mortal Folly" and "Mortal Recoil", noting that, despite the fact that the episodes represented only "the beginning of the show's journey into direct serialization", the story-arc was nonetheless "a tantalizing taste of what's to come."[24] Wired magazine noted it as one of the stand-outs from the Jake vs. Me-Mow DVD, calling it a "three-part suite", which concluded with the third season episode "Too Young".[25] The reviewer enjoyed the way the episode set the stage for the apparent death, resurrection, and de-aging for Princess Bubblegum, which became a major plot point in the next season.[25] Matt Fowler of IGN praised both "Mortal Folly" and "Mortal Recoil", specifically giving applause to the introduction of the Lich, noting that he is "a real, grotesque villain inserted into the merely semi-dark world of Adventure Time".[23] Fowler ended up being very happy with the two episodes, writing that they end the season "strong".[23]

"Mortal Folly" was later adapted as part of a level pack for the 2015 video game Lego Dimensions.[26]

• "Mortal Folly" at IMDb
• "Mortal Recoil" at IMDb