Carly is a woman who appeared only in Five Days of F.L.A.R.G., she and Timmy had tattoos of each other's names put on themselves during the "Amnesia" day of F.L.A.R.G.
When Timmy woke up after the Amnesia day of F.L.A.R.G., he realized he could not remember anything from what Mark Chang described as the best party ever, which was even more strange because he had a heart shaped tattoo with the name "Carly" on it. Later in the episode, as Timmy is trying to run as far as possible to avoid Mark Chang throwing up on him, he runs into an extremely attractive woman named Carly who has Timmy's name tattooed on her shoulder. But just as the two eye one another, Timmy starts running again.
She's a tall brunette wearing a dress, bracelets, and ankle bracelet, and high heels with a tattoo with the word "Timmy" on it.