"[I'm] Balthazar Horowitz, but you can just call me the Ball pit Kid." — Balthazar Horowitz[source]
Balthazar Horowitz, also known as the Ball Pit Kid, is a young boy with dark blond hair. In contrast to Phineas and Ferb, he is an average boy. He has made a large amount of appearances in the show.
Phineas and Ferb use their x-ray specs to find and retrieve him from the ballpit he has gotten lost in (hence his nickname). Oddly, when Ferb pulls him out, he has brown hair and is wearing a black shirt, brown shorts, and mahogany shoes and hat, similar to Buford Van Stomm's color scheme. But in the very next shot, he has his normal color scheme.
Sees Agent P, in the Lawrence robot, placing his "consumed" pies out from the robot's posterior ("Ewwww!"). He later sees Carl talking to Agent P after they bring Lawrence to the picnic. At the very end, he comes upon Perry again and says, "Hey, don't I know you from somewhere?"