Buttercup Utonium Rivera

Buttercup Utonium Rivera has short black hair in a flip, grass green eyes, and dresses in grass green. Referred to as the "tough one" or in the ending theme, "the toughest fighter", she is the group's tomboy, as she is scrappy, tough, stubborn and loves fighting. When it comes to villans, she prefers brute force to thinking things though. Buttercup also prefers her birthday to be in September because thats when colors become darker and it becomes open season.

Though one of the good guys, Buttercup can be mean and extremely insensitive at times, which occasionally makes her the true antagonist of the show. The reason of why Buttercup is mean is that she is secretly insecure and jealous of her sisters. Feeling like she's not as smart as Blossom or as cute as Bubbles (as well as not having special powers alongside them), she tries to make up for it by being the toughest. She bullies Bubbles for her naviety and her "girlish" hobbies and, more than once, refused to obey Blossom's (or The Professor's) authority. Despite her faults, she has a more softer side, for she deeply loves her sisters and would do anything to protect them. She even once had a green, security blanket that would "make her a great fighter" (Cover Up). In "The Rowdyruff Boys", she has a tremendous disdain for resorting to kissing the boys in order to eliminate them, though willingly kisses a boy ridden with what she feared to be "cooties" in a later episode. During the birth of the girls in The Powerpuff Girls Movie, she was initially shown to look extremely happy with wide eyes and an open mouthed smile up to the point where, last of the three girls, Professor Utonium said he would name her Buttercup "because... it also begins with a B". Once she heard this, Buttercup immediately pouted, crossed her arms, and slouched to the side. This may also explain her angry nature. In the episode "Mime for a Change," she can play a magical bass guitar.