Ursula's garden is her collection of merfolk that hang around the entrance hall to her lair. Each one was once a mermaid/merman who came to Ursula for help in some matter, but couldn't afford her high demands, leaving them helpless before her power.
The Little Mermaid
Their second appearance was when Ariel went to Ursula's lair. Ariel was disgusted by the sight of the polyps, but continued forwards anyways. One of the polyps grabbed Ariel's wrist and tried pulling her away from Ursula's lair, but in a fit of fright, Ariel managed to pull her wrist away.
During the song, Poor Unfortunate Souls, Ursula explained the backstory of how all her polyps were merfolk who were unable to pay her price, so she took them as compensation, and if Ariel was unable to complete her side of the deal, she would be transformed along with them. The film also implies that their souls were absorbed by Ursula in the process.
During the battle with Ursula, King Triton was transformed into a polyp when he decided to take Ariel's place in the deal, but shortly after the battle, (when Ursula was killed), he and the rest of the garden were transformed back into merfolk.
The TV Series
The polyps in Ursula's lair were never featured in the show itself, probably due to their frightening appearance, but a creature of similar appearance did appear in the episode, "Tale of Two Crabs". In this, Ursula steals a magical stone which she uses to transform the denizens of Triton's Palace into what she calls, "worms". When she successfully manages to transform King Triton, Ariel, and Flounder, it fell unto Sebastian's rival Zeus to save the day by destroying Ursula's stone.
House of Mouse
In the episode titled, "Pete's House of Villains" Pete hires Ursula to seat guests to their tables, only instead of seating them to tables, she transforms them into polyps. King Triton is the first one to be transformed and see on screen. His apperance being vastly different from his appearance in the movie; what with his eyes being white instead of golden, his crown shrinking with him, and still sporting his white beard.
Fast forward through the episode and Pete is firing Ursula because of this behavior. In annoyance Ursula briefly transforms him into a polyp. He bounces away angrily, saying he doesn't want to see her again. Though later in the episode he appears to have made a recovery.
Little Mermaid NES
In the NES games, the polyps are stationed in the far end of Ursula's lair, in a hallway just before your encounter with her. Because of Ursula's lair being designed as a maze, the polyps serve the purpose of telling the player that they have reached the correct destination and are on their way to fighting Ursula.
All they shall do is point vertically from the position they are in and bite at Ariel, most likely warning her to turn back.
Little Mermaid SEGA Genesis
In the SEGA genesis game Ursula has transformed the entire kingdom of Atlantica into polyps and have scattered them across the ocean. It's up to Ariel of King Triton to free them from the spell.
For the whole game the polyps serve as items to collect. Simply touching the polyps will free them from the curse and return them to their merfolk forms. Ariel's singing is also able to free them as well.
In the game, along with the random polyps Ariel or King Triton have been transformed into polyps and are being held hostage by Ursula in her fortress.
Ariel's Story Studio
In the game, the polyps can be found in Ursula's lair and during the final battle. If the player were to click on them, all that would happen is that they would moan and groan in agony.
In the game, after the final battle takes place the polyps will transform back to normal, and Ursula will have been transformed into a polyp herself.
Little Mermaid 2 Pinball Frenzy
In the game the polyps are the object of one of the minigames featured. In this minigame the you knock your pinball into the creatures, and after two hits they shall be transformed back to normal. The goal is to free every polyp on the board, so that you can free King Triton, who is the final polyp you must rescue.
In Kingdom Hearts, the polyps can be seen in the front of Ursula's cavern in the Tidal Abyss. All they do in the game is watch Sora. They will follow him wherever he goes, but do nothing else. Strangely, after Ursula is defeated the polyps do not return to their original forms, probably due to complications with the hardware.
In Kingdom Hearts 2, King Triton is briefly turned into a polyp and is about to be killed by Ursula, until Eric interupts the act by throwing his spear at her.
In the first Kingdom Hearts manga, King Triton is transformed into a polyp when Ursula uses his Trident against him. The polyps in her garden were all described by Ursula as, "Liars whom came to me for help but couldn't pay the price." When Ursula is defeated, they all transform back into normal merfolk.
- Despite what many may think, the polyps weren't an original concept by Disney. They were taken from the original fairy tale, only there they were guardians to the witch's lair instead of damned merfolk.
- The SEGA genesis video game based off the movie was the first form of media to give Ariel a full poylp transformation, and was the first to give Ariel a non-human/mermaid transformation before the TV series episode that aired in 1993.