Yeah I always found Kling wierd to be honest.... There's a bit of focus on it briefly, where you learn that it's apparently a 100 years old and just appeared out of thin air really.... *Shrug*.
The ones that usually always truely bothered me were the ones that *almost* looked human, but then again - not quite.... Alakazam, Machamp, Jynx, Mr. Mime, Thro and Thwa (or whatever the Hitmonlee/Hitmonchamp Black and White copies are called) and Hitmonlee and Hitmonchan.