She is a witch and Grim Gloom's wife who desires to take over the Kingdom of Jollywood. She is rather obnoxious and spoiled, and whenever she sees something she wants she demands Grim to get it for her by going "I want it! I want it! I WANT IT!!!"
Hildy appears to be the brains of the wicked duo as her husband is not so bright and lacks magical abilities. Aside from Grim's stupidity Hildy loves him very since he always does whatever it takes to give her what she wants. They often baby talk to each other, make kissy noises (closely), and nose kissing.
She is also known to freak out quite easily, especially when she gets dirty or gets turned into something hideous and slimy like a squid or a slug. In the episode "For the Love of Cheese" it is revealed she can't stand slimy and icky things. Every time she is near, touches or sees anything gross she panics like crazy.
Hildy is very slender and has pale skin and short purple-and-pink hair. She wears a purple-and-indigo, sleeveless costume with purple eye shadow, blue lipstick and has a mole on her left cheek.
- Three hundred girls auditioned for the voice of Hildy until Kelly Osbourne got the job which became her debut voice role in an animated series.
- Kelly Osbourne describes Hildy as "Bad with the best intentions" and calls her "My alter ego - my Sasha Fierce".
- Hildy's bratty personality is somewhat similar to the Willy Wonka and the Chocolate Factory character Veruca Salt, shouting and demanding Grim to get what she wants.
- Grim and Hildy's names are derived from Grimhilde, the Evil Queen's alternate name that was given in early publicity materials.
- In the episode "Grim the Genius" it is revealed that Hildy's name is short for Hildegard.
- Hildy shares some physical similarities to her voice actress such as the purple hairdo, however her design wasn't based on Kelly Osbourne as the character was animated two years before she was cast.