Let me restate the "tone" problem, then. In the current game, the rest of the group said they wanted "monster hunters in the dark and grimy streets of Victorian London." This was among a few other proposals, including a wackier, 4-color superheroes game. The other players are trying to hew to fairly realistic characters and keep the tone dark and gritty. MPD-lad, having signed up for the same game, under the same understanding, made a character that intentionally disrupts that tone. The "charm the squirrel" thing is not an exaggeration--this is how he amused himself while the rest of the group tried to investigate why Werewolves masquerading as a group of Irish priests were taking carriage rides into the forest once a month.
Now, when as we're moving to a new game, he's come up with an even wackier character concept. I'm saying no, not so much because I don't want to run a wacky game--I've run them by the dozens--but because all of the other players are taking it seriously, and I don't want them to have their game derailed. Moreover, their characters will probably not want to associate with this character, anyway, so steering him away from that idea will keep tensions at the table a little lighter. Five out of six people at the table want a serious tone; I'm certainly past the stage as a GM where I think I am the god of the table, so it's not just my edict on this one.