Scarlet Overkill is known as the world's first female supervillain. She is a stylish, ambitious, and powerful criminal mastermind who seeks to become the Queen of England by stealing the crown, and she hires the Minions (Kevin, Stuart, and Bob) as her henchmen. Her backstory involves growing up on the streets and in an orphanage, fueling her desire for power and villainy. She built her empire at a very young age and works hard to be the best. She demands to be respected. She gets angry very fast if things do not go her way. She is very good at public speaking. She knows how to charm people and get them on her side. Because she was poor and left alone when she was young, she is deeply afraid of betrayal. She often assumes people are turning against her. She acts nice to her friends, but she expects perfect work. She is willing to hurt people if they fail or make her mad.

Herb Overkill is a supervillain inventor and the husband of Scarlet Overkill. He is a laid-back, groovy character who supports his wife's world domination plans by creating gadgets like a weaponized dress, but he is often overshadowed by her and gets caught up in slapstick situations. He is madly in love with Scarlet, gladly taking her last name and fiercely supporting her ambition. Unlike traditional villain dynamics, he feels absolutely no jealousy toward her success. He is extremely chill, especially compared to his fiery wife. He is the brains behind the operation, engineering all of Scarlet's advanced weapons and gadgets—from lava guns to rocket dresses. Though usually easygoing, he gets deeply upset and protective if Scarlet is ever harmed.