13 Again was an interrim episode made between "Dad's Dungeon" & "Finn & Fionna" in response to fan complaints after the events of "Too Young". Katy Perry guest stars.
Princess Bubblegum's feelings for Finn get the best of her, so she makes a serum that makes her younger (since asking The Lich to possess her is pushing it).
At the castle, Princess Bubblegum is working on the soap serum again. However, she pauses & remembers she was working on it with Finn when she was 13 biologically. She also remembers how she had romantic feelings for Finn in that timeframe & starts regretting her decision to become 18 again (it even brings her to tears). Later that day, Finn comes to report for escort duty. Apparently, the Nut Kingdom has been intercepting shipments between the Candy & Slime Kingdoms after PB threatened all-out war when the Duke of Nuts succumbed to his pudding deficiency. PB tells Finn about her plan, but also thinks it's risky, since Lemongrab would chew her out in an instant & The Lich would easily recognize. Finn administers a speech about how her destiny lies in her own hands, how he would gladly accept the change & that if Lemongrab comes around, he will help her make the Candy Kingdom dirty beyond belief. After commenting about Finn's improving speech-making abilities, she retires to her lab.
That night, PB makes the serum & tests it on Colonel Candycorn, who has recently retired from the Army. It works! Almost. She gets stuck at 16 years old (in her 16-year old form, she is voiced by Katy Perry).
The next day, Finn finds PB in her room, crying. After learning of her situation, Finn promises to help. Meanwhile, Lemongrab arrives, after learning PB is once again underage. Finn & PB remain in the lab to de-age her 3 years further. After perfecting the serum, Princess Bubblegum (in a long, slow sequence) turns back to 13 (voiced by Isabella Acres again). Soon afterwards, Finn & PB kiss.
Lemongrab puts the Candy Kingdom under martial law until an interrim leader (in this case, Prince Gumball) can be installed. Finn & PB, meanwhile, visit the the landfill & request that the waste be scattered around the kingdom. The dump owner is confused, but complies.
Soon, the Candy Kingdom is so dirty, Lemongrab runs off & says PB can keep her leadership. As he runs, Lemongrab runs into a group of Candy Soldiers, who gun him down on the spot. With no kingdom to lead, Prince Gumball, accompanied by Fionna & Cake, return their own Candy Kingdom. Finn gets a funny feeling, which PB notices. PG also notices Fionna's face looks wierd. When asked, both respond (in split-screen) that they sense another human nearby. PB & PG get worried & lead them away from each other.
That night, Finn & PB see a ship off. The ship is bound for the Land of Aaa. Fionna, Cake & PG are aboard, though Finn is unaware of Fionna's presence. A discussion between Finn & PB reveals that PB had always had regrets regarding becoming 18 again, and that she always loved Finn afterwards, but was too afraid to say something due to their age differences. As the episode ends, Finn & Princess Bubblegum kiss again, sealing the deal.
- Finn: Jeremy Shada
- Princess Bubblegum: Hynden Walch (18-years old), Katy Perry (16-years old), Isabella Acres (13-years old)
- Prince Gumball: Neil Patrick Harris
- Fionna: Ashley Johnson
- Lemongrab: Justin Roiland
- Dock Worker: Frank Welker
Cake appears, but does not speak.
- Regret/13 Again - First part heard at the beginning of the episode when Princess Bubblegum flashes back to the time when she is 13. Second part heard after the transformation and when Finn & PB kiss.
- Transformation - Heard when PB looks back on the days when she was 18 & when she transforms.
- Love Theme - Self-explanatory.
- This episode's purpose is 4-fold:
- To tide fans over until The War Chronicles.
- In response to the events of "Too Young"& "Adventure Time with Fionna & Cake" after mass fan complaints
- As a lead on to "Finn & Fionna"
- Hynden Walch was released from her contract early to voice Starfire in a new "Teen Titans" TV Series
- Finn & Princess Bubblegum's status as a couple is made official.
- A behind the scenes video released on Youtube shows the chain of command (AKA Princess Bubblegum's voice actress) being handed down as the voice acting session goes on.
- Katy Perry guest stars as 16-year old Princess Bubblegum.
- Fionna, Cake & Prince Gumball make cameo appearances, though only Fionna & PG speak.
- Jake is completly absent in this episode, a first for the series.
- This episode features the smallest cast of characters to date.
- Isabella Acres returned after she was released from her other duties. She will now be the official actress for Princess Bubblegum.
- Music from "Doctor Jekyll & Mr. Hyde" is heard during the first tranformation. In the second transformation, music from "Doctor Who" is heard.
- Princess Bubblegum's transformations are identical to the regeneration process from "Doctor Who". Ironically, the "Doctor Who" music heard when PB de-aged to 13 was also heard when the Tenth incarnation of The Doctor (Played by David Tennant) regenerated into the Eleventh (Played by Matt Smith).
- This episode confirmed that the gender-swapped characters exist in the same universe as the regular characters, and that Finn is not the last human.
- Despite leaving the role of Princess Bubblegum, Hynden Walch will still voice Gum Drop Lass #1.
- This episode officially voids Ice King's fanfiction & hints at the cover-up detailed in "Finn & Fionna." It also makes "Incendium" non-canon (within The War Chronicles spin-off series).
- This episode reveals that the Land of Ooo has started a new technological renaissance, as a truck and several HMMWVs (Humvees) are shown. Also revealed are tensions between the Candy and Nut Kingdoms.
- This episode considered part of The War Chronicles spin-off series and not the main series.