Princess Bubblegum accidentally causes another zombie outbreak in the Candy Kingdom. But when the princess herself is zombified, it's up to Finn, Jake, Lady Rainicorn, and Lumpy Space Princess to follow Bubblegum's notes and whip up an antidote.
Tropes:
- Arson, Murder, and Jaywalking: The zombies have muscles, wings... and beautiful lips?
- Assumed Win: Amusingly, the win is on the assumption of the audience, rather than one of the characters.
Princess Bubblegum: Finn the Human!
Finn: Yes?
PB: Will you please move out of the way?
(Finn does so, allowing PB to award a medal to Science the Lab Rat)
- Big "OMG!": Finn drops one when he recognises the direness of his situation:
Finn: Ohhh, MYYY GLOOOOOB!!!
- Cerebus Syndrome: This time around, the zombie thing is played more seriously.
- Continuity Nod: "From Bad To Worse" features the zombie virus from "Slumber Party Panic". The difference from the latter is that Princess Bubblegum is unable to create the antidote.
- Darker and Edgier: This episode is "Slumber Party Panic"'s Zombie Apocalypse theme up to eleven.
- From Bad to Worse: It's the title. The theme of the episode is that the situation gets worse and worse as time goes on, thanks to the heroes' botched attempts to reproduce Bubblegum's zombie antidote.
- Halloween Episode: The second of a two parter.
- His Name Is...: Princess Bubblegum is zombified while trying Finn how to make a cure "Just let Science do the work! Science is... maaaaaaa raaaaaaaa..." It's not until near the end of the episode when Finn finally figures out that she was trying to say: "Just let Science do the work! Science is my rat!"
- Intellectual Animal: The "twist" in the episode: the lab rat, named Science, knows how to make the zombie antidote and can coach Finn through the steps by nudging various books and flasks.
- Our Zombies Are Different: The zombies end up winged, muscular and with Gag Lips as a result of the heroes' botched antidotes.
- Sequel Episode: One for "Slumber Party Panic", being much Darker and Edgier than the last one.
- Shout-Out:
- The "TS-19" label on Science's tank is a reference to the zombie TV series The Walking Dead, in which "Test Subject 19" is plot-significant and "TS-19" is an episode title.
- Jake's hand becoming infected refers to Evil Dead 2.
- Tempting Fate: Starchy is up on a rooftop, glad that he's far away from the zombie hordes... then he gets nabbed by one of the flying zombies Finn accidentally created.
- Too Dumb to Live: Cinnamon Bun causes the zombie apocalypse by eating preserved zombie flesh from the previous outbreak. Lady Rainicorn too.
- Undeath Is Cheap: The infection can be cured with a formula PB created, although it does not give immunity to the virus, as the other zombies turned Jake back the second he was cured.
- What Happened to Mommy?: On an absurd level. Even though zombie Jake is not in any danger of dying permanently and will certainly attack her at the first opportunity, Lady Rainicorn still smiles at him, frees him and hugs him lovingly. She obviously gets infected and turns into a zombie.
- Zombie Apocalypse: On a much larger scale than last time.
