|The following information is from the Adventure Time comic book series.|
It may not be part of the same canon or continuity as the animated series.
Issue 20 of the Adventure Time comics.
"It’s another crazy adventure with our favorite heroes of Ooo. Join Finn and Jake as they protect their friends from the Ice King…who isn’t really a bad guy…he’s just kind of sad sometimes. But that’s okay because Finn and Jake aren’t sad, and that’s what makes them our heroes! Jump into fantastical world, with adventures, lessons, and sometimes princess farts."
An unknown person shown in a first-person perspective goes to visit Finn and Jake and they look at Ooo through a telescope until a Gumball Guardian, with Ice King inside of its dome, attacks the Tree Fort and captures Finn and Jake. Ice King claims he is just going to mind control it for a little bit just to see what it's like to be big, but he lost control.
Jake gives the person his and Finn's "Adventure Tome," which has all sort of information such as good places for adventures, a list of enemies and frenemies and a list of Finn and Jake's favorite fighting moves. The person remarks that the book was useless to help the situation.
The person is able to get inside the Guardian and hit its reset switch, releasing Finn, Jake, and Ice King. Ice King explains he used a mind control enchantment that allowed him to make the Gumball Guardian obey two commands. After he made his first request of knowing what's it like to be big, he told him "Who cares? Go do whatever! Go nuts!", thus creating the problem. It is then heavily implied that Finn and Jake planned this with the Ice King to give the person an exciting afternoon, though they defensively deny it and give the person the Adventure Tome as they leave.
As the person returns home and gets ready for bed, it is revealed that the person is, in fact, Princess Bubblegum and today was her birthday.
Back up story
Billy! Grocery Time Part 1
The Birthday Kingdom was having the greatest party ever when they ran out of ice cream. As crisis erupted, Billy flew to the Grocery Kingdom on the Ancient Psychic Tandem War Elephant to get more ice cream. As he reached the Ice Cream Peninsula, he found it overrun with Avocadobots led by the notorious Ham-Pire.
Billy! Grocery Time Part 1
- Birthday Princess
- Birthday Peeple
- Ancient Psychic Tandem War Elephant
- Party Bears
- Dr. Donut
- Mr. Cupcake
- Ice King
- Flame King
- Flame Princess
- Earl of Lemongrab
- Peppermint Butler
- Gnome Ruler
Additionally, multiple food products from past episodes are visible in the Grocery Kingdom, including:
- A younger Flame Princess can be seen in one panel, showing that Flame King would let her out of her lantern from time to time.
Comic preview pages and panels