If he were to refer to a fancharacter I made as "Master Leonardo" or "Master Alphonzo," that would be good.
If I were to come to Foster's, he would refer to me as "Master James." But in my fanfictions, he would refer to me as "Master JRuff."
According to PBL's last post, I should ask why he refers to most of the female characters in the show by the title, "Miss" so and so.
But still, I think Mr. H is quite okay for a rabbit with a good sense of humor.