He has a habit of drastically increasing his pitch whenever exclaiming certain words, such as "Activate!!".
He seems to be a certified attorney.
Fastidious first appeared in the episode "Neat Freak". He ran into Yin at the store "Battle, Bath and Beyond", where (after cleaning her up) he told her of his woes in dealing with the trio known as the Filth Spirits: the Wet and Soggy Spirit, the Windy Weather Spirit and the Mud and Slime Spirit. Feeling sorry for him, Yin convinced Yang to help, with the both of them thinking that they were doing good. In reality, he was using them to capture the spirits so that he could destroy them via an incinerator. Thankfully, Yang saw through his ruse and (unbeknownst to his sister) stole the Spirits and, after revealing his own deceit, freed them on Fastidious. His Hamsterbot was wrecked in the ensuing fight against the combined forces of the Woo-Fu Knights and the Spirits and, eventually, he was flushed down his own toilet.