Catgirl's outfit is very similar to her male counterpart. The original suit is nearly identical. It features an yellow and orange form-fitting suit with the Catman emblem on the front, an orange cape, and an orange mask with fake Cat Ears. The mask is slightly different, as it doesn't feature a fake cat nose and whiskers. The Catgirl suit also is absent of a tail like Catman's.
Since it was made for an adult woman, the suit didn't fit Chloe at all when Catman forced it on her in Whittle Me This. So Chloe spent the episode wearing only the mask and cape.
In Nuts & Dangerous, the suit appears to have been remade at least in part for Chloe. This suit differs from the original, the form-fitting suit is replaced with a yellow and orange sundress, with black leggings.
Catgirl was apparently Catman's partner from his TV show. The original Catgirl was an African-American female, nothing else is known about her, as she was only shown briefly in photo.
In Whittle Me This, upon meeting Chloe, Catman mistakenly believes that she is the Catgirl from his TV show (Even saying that she looks exactly like she used to), and that Timmy had tracked her down for him. He forces the costume on her, which doesn't fit her. The situation escalates when Catman thinks Timmy has been kidnapped by yet another character from his TV show, "The Whittler". He then assembles a team consisting of Himself, Catgirl, Mr. Turner, Denzel Crocker (The Falcon), and Mr. Turner's pet monkey Chaz to rescue him.
Chloe reprises her role as Catgirl in Nuts & Dangerous, in a movie by the same name directed by Mr. Turner.
As Catman is a parody of DC Superhero Batman, Catgirl is a parody of Batman's female counterpart Batgirl.
The original Catgirl is African-American, but in the comics, Batgirl is Caucasian and a redhead.