*Princess Undina is a character that appears in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. She is an aquatic mobian fish and the princess of Meropis.

Undina is a mobian fish of average height. Taking after both of her parents, she has violet skin, purple eyes with thick eyelashes, a white muzzle and a fairly rounded face. She has small round fins on the sides of her head and on her ankles, an esca on her forehead and a thin, long tail fin. While they are not always visible, she is usually depicted with fangs.

When it comes to her attire, she has a taste for gaudy and elaborate outfits with more than a few accessories. Her most prevalent outfit consists of a sleeveless yellow blouse held together by a deep pink gem set in cyan, which opens to reveal her midriff, with cyan lining, over a black crop top and tight, black short shorts, along with a matching pair of yellow sleeves held together by thin cyan bands with matching cyan linings, a yellow hairband with a ribbon on the left side, a deep pink ring on her right index finger and a cyan ring with a pearl on her left middle finger. She also wears what looks like big circular white earrings on her head fins, green eyeshadow, and a pair of deep pink single-strap sandals along with matching leg straps.

Before meeting Honey the Cat, she was shown to have the scales on her head tied together with a small gold crown, and she wore a very simple yellow sleeveless dress with deep pink oval spots on the skirt, along with an armband and a matching pair of bracelets.

When she first appears, Undina is presented as being akin to a stereotypical valley girl: ditzy, somewhat airheaded, and seemingly unaware of situations taking place around her. She frequently insisted that others simply refer to her as Deena, instead of bringing attention to her royal title. She also showed no compunctions about assisting her kidnappers, instead treating the pirates as if they were her friends and happily going along with Shellbreaker's orders, even going so far as to suggest ransoming Echo when she found out the Lieutenant had come to rescue her.

However, Undina is later revealed to be quite clever. She admits to the Chaotix, Echo and Razor that she knew she could get away with more if her captors thought she was not worth paying attention to, and by pretending to be much less intelligent than she actually was, as well as making a series of seemingly random observations, such as recognizing Espio from a tournament match, she managed to keep her rescuers safe and stop the pirates from hurting others. She also managed to convince Echo to be her bodyguard by pointing out that, while she was safe, her parents would appreciate the added security.

She is shown to be unfailingly kind and polite, even to her enemies, showing outrage at the notion of leaving Shellbreaker's crew to starve so she can escape from them. In spite of this, she can also be somewhat shortsighted, not considering the consequences of leaving school to see the world without telling anyone or how expensive it would be, and failing to recognize that a group of pirates would be power-hungry and untrustworthy.*