Shirley

Shirley was a villain, who was created by Billy, Mandy and Timmy. He was created in the crossover special, The Grim Adventures of the Fairly OddParents 3.
Although he is classified as a villain, he is actually very humble, polite and friendly and any evil action he performs is usually followed by a "Swell", "OK" (after asking if he can go ahead with his scheme) or "Awesome".