The Kid (Codename: Kids Next Door)

The Kid also known as "Ace", is a slender mysterious Hispanic character whose name is unknown(although may be numbuh one due to his shades being the same as numbuh one's(EDITED BY ANONYMOUS)), is meant to be very cool and says that he works alone. He first appeared in Operation: D.O.G.F.I.G.H.T., as a rival pilot to Numbuh 2 and did not speak until the near-end of the episode when they cross paths in Mr. Washer Hobby Shop when he asked for a defense system upgrade. By the end, he and Numbuh 2 had destroyed each other's aircrafts and realized what Mr. Washer had been panning, so they worked together in order to stop him.

In Operation: C.A.K.E.D.-F.O.U.R. he was a part of the Toobathon to win the Delightful Children's birthday cake. At one point he slows down to talk with Numbuh 3 about "sharing decorating tips" after the race. This suggests he might have a mutual attraction to her, but is not confirmed otherwise.