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.
- 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!
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!!!
- Call-Back: "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.
- Cerebus Syndrome: This time around, the zombie thing is played more seriously.
- Darker and Edgier: This episode is "Slumber Party Panic"'s Zombie Apocalypse them 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.
- 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!"
- Our Zombies Are Different: In the end, they're winged, muscular and have Gag Lips.
- Sequel Episode: One for "Slumber Party Panic", being much Darker and Edgier than the last one.
- Too Dumb to Live: Cinnamon Bun causes the zombie apocalypse by eating preserved zombie flesh from the previous outbreak.
- 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?: Lady Rainicorn can't stop herself from letting Jake out of the shower even though he's clearly infected.
- Zombie Apocalypse: On a much larger scale than last time.