Slime Princess (also called SP) makes her first appearance in "Prisoners of Love" where she is kidnapped by Ice King. She showed a lot of affection to Finn, even going as far as saying she wants to marry him for saving her and the other princesses, or at least until Jake told her that Finn "wets his pants constantly, all the time." She reappears in "Loyalty to the King," where she is the first princess to meet and befriend the "Nice King" in the park after misinterpreting his real name. And she again appears in "Video Makers" where Finn decides to use her in a scene for his movie where she does stunts around a river filled with alligators. Though she accidentally fell in the river, she ended up kissing the alligators instead of getting killed, ruining the scene for Finn. She also appears at the premiere of the film at Finn and Jake Movie Club. She is the ruler of the underground Slime Kingdom as shown in "Love Games." In "Princess Day," she and Breakfast Princess argue about their kingdom trade of one sugar for four eggs, then Breakfast Princess tells her she has an egg in her already, despite her saying that she is an artisan and that she can't just pop one out on command. This episode also reveals she is considered a registered princess. As revealed in "Elemental," she is the current Slime Elemental.
Slime Princess looks just as she sounds, like a glob of slime. The majority of her body is dull lime-green color, but she also has a yellow center. She has two arms, that when not being used may disappear back into her body. She wears a tiara similar to that of Princess Bubblegum, only the gem in the center is green, while Princess Bubblegum's is turquoise. when she has an egg in her it appears under her face in the her yellow center.
After Patience's mega-spell, Slime Princess grew in size, but still retains almost all of her physical features, though she lost the ability to speak English.
In "Princess Day," it was revealed that she has the ability to pop out eggs from her body and trades them with other kingdoms. However, it was also revealed that she is an artisan and cannot just pop out eggs on command. It is unknown if other Slime People can do this as well.
Since "Elemental," Slime Princess has learned to spew slime out from her hands.
She was seen to be using the powers in "Jelly Beans Have Power."
In "Slime Central" she is shown in her elemental form. She was shown to turn others into slime elemental people. The slime elemental people were seen to be party animals and dancers. Slime Princess lost her memories while in her elemental form. While in her elemental form she would absorb others into her and they would appears to be vanished (or dead). In "Skyhooks II," when Lumpy Space Princess fixed Ooo back to normal, everyone who was absorbed into her were revealed to be alive.
- Her tiara resembles Princess Bubblegum's, which has the ability to block the telepathic power of the Lich. It is unknown if Slime Princess' has a similar ability.
- She is Pendleton Ward's favorite princess because she has a "hot lady voice."
- She was once rescued from the Ghost Ship Vortex by Finn and Jake, shortly before the events of "The Eyes."
- She is one of the princesses that Ice King finds to be his favorite as shown in "Princess Monster Wife."
- However, his lyrics in "Oh, Bubblegum" indicate that he thinks she's just "alright."
- According to CN Latin America, she wishes to be the ambassador of the animal kingdom and she fears salt. The latter fact may stem from salt being able to kill snails and slugs, which produce slime.
- In her elemental form, her body resembles Jabba the Hutt's from the Star Wars franchise.
- "Ricardio the Heart Guy"
- "The Eyes"
- "Video Makers"
- "Princess Monster Wife"
- "Princess Potluck"
- "Bad Little Boy"
- "Princess Day"
- "The Music Hole" (pictured)
- "Jelly Beans Have Power"
- "Bespoken For" (flashback)
- "Skyhooks II"
- "Come Along With Me"