Embryo Princess is a princess who briefly appears in several episodes. In the episode "The Lich," the gem from her crown is taken by Finn and Jake with a pair of tweezers as she sleeps, to unlock The Enchiridion. She apparently has some sort of telekinetic power that enables her to create a bubble around her, which resembles an amniotic, sac-like ball. According to the events in "Princess Day," she is a registered princess. So far in the series, she does not have any speaking roles.
Embryo Princess resembles a human fetus. She wears a golden tiara with a magenta stone in it, similar to the tiaras of Princess Bubblegum, Slime Princess, and Princess Princess Princess' monster head. She does not seem to have any clothes on, and her purple veins are visible through her skin. She also has a pink, jelly-like bubble surrounding her body. Her current design is different than in her first cameo.
As seen in "Loyalty to the King," her phone resembles a small pink cube.
This is likely a pun on "cell phone" in that it is literally a cell.
Like most minor princesses, Embryo Princess has had many accidental changes in her appearance throughout the series. In the episode "What is Life?," her telekinetic bubble is blue and round when it is supposed to be pink and globular. She also has no gem on her crown. In the episode "Jake the Dog" her gem is light blue when it is really supposed to be magenta.