Nicole greatly resembles her oldest son, Gumball, who is, like her, a cat. She has light blue fur, and is somewhere between Richard and Gumball in height. Her head is shaped similarly to Gumball's, except Nicole's whiskers are shorter than her son's, and she has visible eyelashes. The inside of her mouth is light pink and her tongue is pink, and her nose is pink.
Her usual outfit consists of a white collared shirt with a button that symbolizes the Rainbow Factory, where she works. She wears a short, light gray skirt to go along with it. Like the rest of her family (excluding Anais and Darwin), she spends most of her time barefoot.
In Season 3, Nicole's eyes are permanently round along with the rest of her family.
Nicole cares deeply for her family, so much that she would do anything to express her love for them. She is also very protective of her family, as seen in "The Ape." Since she is the only truly responsible member of the family, Nicole does most of, if not all the household chores, and in addition, she works long hours at the Rainbow Factory just to put food on the table.
Unfortunately, Nicole also suffers from a tremendous amount of emotional stress because of her many duties. She is also quite the demanding mother and sometimes has an extremely nasty temper that can turn her into a very scary person when upset sometimes. In fact, on one occasion, Gumball decides it'd be easier to face a giant T-rex than an angry Nicole. Despite all that, Nicole is still very benevolent, kindhearted, sweet, and has a softer side at times, and she still loves her family very much, especially her son, Gumball.
Nicole can be quite stern when provoked, and occasionally vindictive, as was shown in the episode "The Ape" after Miss Simian called her and her family "losers." On top of this, she has also proven to be very resourceful and inventive, a trait she most likely passed on to her daughter Anais, who has demonstrated similar talents, in this case, strategically setting a mine-like trap in a paintballing arena/forest merely using environmental supplies and whatever she took with her. Winning seems to be a necessity for her at times, possibly indicating that she is slightly obsessive. Though, despite her somewhat ruthless faults, she can accept defeat, acknowledge her mistakes, and even find humor in them.
Nicole also doesn't like losing, as shown in "The Game."
Nicole is very athletic, and is fully capable of chasing her children across the neighborhood when they are in trouble, as shown in "The DVD." On one occasion, Gumball compared her to a ninja. In "The Remote," she displayed great skills in martial arts, that allowed her to defeat Richard and her sons, and jumping between roofs. Also, in "The Fight," Nicole defeated Mr. Rex and destroyed his house, and in "The Pizza," she defeated some apocalyptic Elmore citizens when they turned against her and her family.
When angry, she is significantly strong, enough to destroy a door, and can fight and defeat anyone, and completely scare people with her rage. In "The Egg," she can completely transform herself into a red demon-like being and eat any person. Along with this, Nicole can make people fear and do what she wants without a question. Like in "The Castle" and "The Limit," just with one penance stare reduces her victims into a horrified state. In "The Vacation," she can completely burn Richard's marshmallow by just looking at it. In "The Finale" and in "The Money," she can also transform into a hulking version of herself.