J.D. is a cool, rebellious biker chick whose best friend is her equally hip robotic bike, Spitfire. They are inseparable best friends. Robot and Monster have crushes on J.D., yet Robot has shown possible interest in Spitfire.
Though very close, their personalities contrast greatly, as J.D. is more vigorous and is willing to put her fighting skills into good use while Spitfire is much more intelligent, serene, responsible and laid-back, willing to allow her best friend to obtain most of the action, as revealed in Biker Girls.
In the episode Biker Girls, it is revealed that J.D., during her stay at Robot and Monster's apartment after a fight with Spitfire, is a slob as she accommodates the boys' bedroom for herself. She's quite messy and irresponsible, hoarding food from their kitchen and leaving it trashed for Robot to clean (and for her to ruin it once again).
Spitfire confirmed this habit of hers when she confessed how she, after their fallout during the episode, had woken up to see her kitchen clean and in good supply of food for the first time. Although an expert in fighting, J.D. is quite dependent on Spitfire, her only source of transportation as she dreads walking.
Other than being very close, they are good friends to Robot and Monster, willing to aid them in troubling situations such as when Robot nearly placed the blinking light factory in jeopardy in Blinking Light. They performed the same act of loyalty when Robot was was accused of 'third degree litter' in Litterbug, determined to hunt down the criminal and save their friend from a 'slap on the wrist'.
J.D.'s sweet, bubbly attitude can usually brighten things the least bit just as Spitfire's calm, playful attitude is able to lay sympathy and sometimes encouragement to those who are down, especially Robot.
JD is a type of aquatic Monster with ocean blue skin and fin ears nearly resembling her to a fish. Her physique is very massive, making her an expert in fighting such as slamming her enemies onto the ground with her own body as shown in Biker Girls. She wears a pink shirt with a heart and crossbones, a blue skirt with white underwear slightly exposed, and black boots.
Spitfire is a red robotic bike with a blue light on the front of her chest. She has handle bars on her head and moves with one wheel.
- Spitfire has the same voice as Cree Lincoln from Codename: Kids Next Door.
- J.D. is the first aquatic Organic seen on the show. The second to appear is Uncle Kuffley in Speeding Ticket.
- Spitfire is the first female Mechanical on the show. The second to appear is Lucy in Ogo's Friend.
- Like Gart, Spitfire has four-fingered hands.
- Like Robot and Monster, they often hang out at the Makin' Bacon as well.
- In Biker Girls, it is suspected that their may be slight attraction between Spitfire and Robot, despite how he had even told her how pretty J.D. is, and Spitfire not showing much reaction to the statement but a little jealousy as shown in Model Citizen.
- In What JD wants, Spitfire gets upset because Robot likes JD. Spitfire might like Robot.
- J.D. revealed that she has a degree in Chemical Engineering in Model Citizen.
- J.D. is, perhaps, one of the tallest characters on the show.
- Many fans prefer Robot to be with Spitfire rather than to be with J.D. In some episodes, it appears that the two mechanics have an attraction for each other.
- Spitfire's original name was going to be Viper, but when the Kung Fu Panda series was in production, they already had a Viper.
- In The Super Pole, Spitfire managed to win everything from Perry, including his dignity.
- In Nobody Panic, Spitfire falls in love with one of Robot's inventions.
- Spitfire shares her name with a My Little Pony: Friendship is Magic character.