Fastidious J. Spiffington is a recurring villain from the Jetix series Yin Yang Yo! He is a small hamster with a cultured British accent, obsessed with cleanliness and world domination. Fastidious is nearly always seen inside a hamster ball that serves as the control center for his robots, mainly his Hamsterbot. He has a habit of drastically increasing his pitch whenever exclaiming certain words, such as "Activate!!" He seems to be a certified attorney. Fastidious made his debut appearance in the episode "Neat Freak", when he ran into Yin at the cleaning store. He managed to goad Yin into capturing a trio of elemental spirits, and nearly succeeded. However, Yang was able to find out Fastidious was the real evildoer, and with the spirits' help, the rabbit twins beat Fastidious.
- There is a Running Gag about Fastidious claiming himself as a hamster despite anyone saying that Fastidious being a gerbil.
Fastidious is a Hamster With Yellow Fur, blue cutting a hornet like $100 down the yellow Cottontail with stripes and Black Whiskers, Light Cyan Rings Around her left Eye, One Purple Eye just Like Yang and One Cyan Eye, Pink Nose, and Wears a PJ Suit with a White collar and a red bow.