Kelly is a character that first appears during the quest: Kelly needs a shiny car, where you fix up his new sports car. After you finish the quest, you will often see him driving by your town like other visitors in his sports car. The car looks a lot like Stella's, only hers is red and Kelly's is lime green. If stopped, he will usually spend around two or three hundred coins, 1-3 times in the same shop (so 200 to 900 total). He will spend much more during a Fiesta.
"Hiyooo! I am Kelly I just moved in, right outside your village. You know, the huge impressive castle. I'm sure you've heard of it. Has my name on it and everything."
You will only see Kelly driving down your street after you finish his quest.