Ken Anderson drew many different designs for Medusa, including a Lauren Bacall-esque "grande dame" (with snake-like locks of hair, true to her name), a vain, sinister, slender lady and a portly woman with a facade of make-up, in an attempt to find the right personality. The design eventually settled on a hideous appearance (of which she seemingly remains unaware), with an excess of makeup, sagging breasts, green eyes, and wild, fiery red hair to suit her fiery personality.
For a small amount of time early in the film's production, the Disney story team was heavily considering reusing Cruella De Vil from their 1961 classic, One Hundred and One Dalmatians. Drawings by Ken Anderson depicted her in alligator skins, suggesting that she would have visited, or had dealings with, Devil's Bayou. (John Canemaker, "Before the Animation Begins: The Life and Times of Disney inspirational Sketch Artists") This idea was abandoned, as the studio was not interested in producing sequels at the time, and Madame Medusa was created. Cruella and Medusa share certain characteristics, including fixation on a single goal, a fiery temper, vanity and a tendency to drive recklessly.
Medusa is loosely based on the Diamond Duchess, an elderly woman who served as the villain in Margery Sharp's original novel, Miss Bianca, and who similarly wanted to obtain a specific diamond and was using an orphan girl in her plan (named Patience in Sharp's novel). However, Medusa has a somewhat wilder, more eccentric personality than the Diamond Duchess.
In addition to inheriting some traits from Cruella, Medusa may well have passed on of her traits on to Ursula, including a similar appearance, and the possession of 2 scaly green pets (Brutus and Nero for Medusa; the Moray Eels, Flotsam and Jetsam for Ursula).
Medusa's name most likely comes from the Greek mythological monster of the same name. The monster had snakes for hair; the Disney character has normal red hair, which nonetheless looks rather snaky. Whenever the Rescuers character stares at Penny, the girl freezes temporarily; whoever looked the Greek monster in the eye would turn to stone.
Medusa is described as a greedy and obsessed person. She is completely fixated on diamonds; when we first see her pawn shop, there is a prominent sign advertising half rates for people who bring in diamonds, and though she could have made a lot of money on the assorted pirate treasure in the cave, she brushes it off because the Devil's Eye, the world's biggest diamond, is the only thing she's after. She is also very crazy, ill-tempered, and sometimes unstable, which makes her intimidating at times. However, she has a bit of a bumbling nature, which makes a little hard for people to take her seriously as a really scary villain. She is very intelligent and patient, but when she comes to the point of losing it, she is not someone you want to be around. She will stop at nothing to get what she wants; such as using Penny, a little girl, to go down into a dark cave just to retrieve the Devil's Eye. Her greed and obsession with the diamond led to her ultimate downfall when she double-crossed Snoops and treated her pet crocodiles very cruelly, resulting in Snoops' abandonment and Brutus and Nero attacking her instead.
Prior to the film, Medusa discovers that the world's largest diamond named the Devil's Eye is buried deep underground in a pirate's cave in Devil's Bayou. Much to her disappointment, the cave entrance is much too narrow for her to fit through. Neither her incompetent henchman Mr. Snoops nor her two pet crocodiles Brutus and Nero can fit through it. It is then that she decides to return to New York, where her pawn shop is located, and captures the poor orphan Penny to fetch the diamond for her.
Three months later (when the film introduces her), Medusa finds that although Snoops has managed to force Penny down into the cave, he is unable to persuade her to search as she was too worried about drowning and her teddy bear getting wet. Moreover, he has caught the little girl sending out messages in bottles. Medusa, frustrated with Mr. Snoops' inability to manage an orphan girl, takes the next flight back to Devil's Bayou to take charge herself.
Upon arriving, Medusa made things even more miserable for Penny, so much so that Penny attempted to run away numerous times, only to be caught by Medusa and her two faithful crocodiles every time. Medusa lost her patience with Penny and declared that no matter what, Penny would find the Devil's Eye, and would stay underground until she did so, regardless of the danger. Prior to their search, Bernard and Miss Bianca from the Rescue Aid Society in New York arrive to try to save Penny, but Medusa panics upon the sight of them and nearly blows them away with her shotgun. This fails, however, as the two mice escape and soon afterward meet Penny face-to-face.
She ultimately forces Penny down into the cave, holding her teddy bear hostage, and refusing to lift her back out until she has found and retrieved the diamond. Since the cave fills with water at each high tide, Penny was aware that Medusa's threat was a potentially lethal one. She was accompanied by Bernard and Miss Bianca and with their help, she found the Devil's Eye. Unfortunately, it was stuck in the skull of a dead pirate and they could not get it out, but Medusa refused to hoist Penny up until she retrieved it. With the tide rising and the waters splashing violently, Penny and the mice recovered the diamond by opening the skull with a sword and were lifted back to the surface just in time. Medusa immediately indulged in her newfound wealth, refusing to let Snoops so much as a look at it, despite his pleas that they were partners and wanted an equal share. The group made their way to the riverboat where Medusa planned her escape.
While Miss Bianca and Bernard called their swamp friends for help, Medusa held Penny and Snoops at gunpoint, intending to escape with the diamond herself (which she hid in Penny's teddy bear), threatening to kill Penny and/or Snoops if they tried to follow her. However, the two mice literally trip Medusa up, allowing Penny to grab her teddy bear with the diamond inside and make a run for it. Medusa is then attacked by the swamp critters (Luke prodding her in the bottom with his pitchfork), and is forced to use her shotgun against all of them, only to soon have that option removed when her shotgun was plugged up and backfired when she tried to fire it again. Medusa and her crocodiles fought the animals slowing her down, but were easily overpowered, and was soon at the mercy of Mr. Snoops' fireworks after the animals set them off.
Penny fled in Medusa's swampmobile, but Medusa refused to give up and pursued Penny by water skiing. She nearly had Penny at one point, grabbing hold of the back of the seat on the swampmobile, only to get her hands soundly smacked by Ellie Mae, forcing her to let go in pain. She ran into her two crocodiles and whipped them with a rope to get them to move faster, much to their anger. However, the rope broke and Penny was able to escape and Medusa was sent flying into her riverboat, which was now sinking due to the fireworks display, crashing into one of the smokestacks and hanging on for dear life. Medusa watched in defeat as Penny and the animals escaped with the Devil's Eye, leaving her to face the angry Brutus and Nero alone while Mr. Snoops, all tattered and torn, fled the scene, all the while laughing at Medusa's misfortune.
It is unknown if Medusa was able to escape the angry crocodiles, although it's implied that she never escaped this time and was presumably killed by them in revenge for her mistreatment of them.
Medusa made a few cameos in the animated series and was seen in a crowd shot in Mickey's House of Villains.
- Medusa is one of the 10 villains featured in the tongue-in-cheek Disney Villains: The Top Secret Files. Medusa's section of the book includes a photo of Nero and Brutus as babies and a catalog of the world's greatest diamonds (most of which Medusa has scrawled 'too small!' over). Medusa is ranked as the ninth greatest Disney Villain at the end of the book.
- It has been noted that Madame Medusa and Ursula share a similar facial structure.
- In early concept art, Madame Medusa was going to live in a derelict mansion rather than a half-sunken steamboat.
- Actress Geraldine Page who provided the voice of Madame Medusa was married to the actor Rip Torn. In 1997, 10 years after Page's death of a heart attack, Rip Torn provided the voice of Zeus in Disney's Hercules.
- Both Medusa and McLeach end up being chased by crocodiles.
- Disney based Medusa on The Duchess of Diamonds from Margery Sharp's novel.
- The car Medusa speeds away in is very similar to Cruella De Vil's.
- Medusa is one of the few green-eyed redheads in the Disney universe.
- Madame Medusa was named after the Greek mythological creature, Medusa, which had the power to turn anyone or anything, who looks into her eyes, into stone and was later defeated by Perseus.
- The role of the antagonist in The Rescuers was going to go to Cruella De Vil but went to Medusa instead. Despite this, Medusa does share similarities to Cruella de Vil.