Mondo is a character that unfortunately only appeared in the Japanese CD drama with the name "A white tomorrow" (I'm pretty sure that was the one). Those will probably not make it over the Pacific, (I mean, they are HOW old now?), but it is rumored that his English dub name would be Billy (like in "the kid"). He is probably somewhere between 13-16 years old (he's said to sound older), and his job is to assist other Team Rocket agents, at least Jesse and James. He drives a red jeep, gives them lunch (well, some rocket meal) and loves Meowth. He actually loves Meowth to the limit of trading him for his own Ditto, something the feline isn't too pleased with.
He has a crush on Jesse and both of them are like gods to him, and... yeah. I think that's more or less all there is to him. He looks really innocent and probably is too.