|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.
Agent Princess (also known as "Arsonist Princess") is a princess and a vigilante freelance who first appears in Adventure Time: Candy Capers Issue 4.
When Agent Princess lost all her money at the Casino Castle, she proclaimed that the casino was rigged to cheat and went undercover to stop them (when in fact the casino was completely legitimate). After she caused Bad Guy Magpie, the Casino Castle's owner, enough trouble, Peppermint Butler ended up getting restrained by her and put on a death trap under the belief he was Agent Princess in disguise. He was rescued by the real Agent Princess who reveals she rigged the casino explosives and destroys the casino.
She later returns as the demolitions expert in Peppermint Butler's siege of the Vault King's lair.