um, I still sometimes try and act more like Spike from Cowboy Bebop. Honestly the character is just so cool, and if I happen to sit up at night watching a few episodes, I suppose it affects me.
That is not a particularly violent show though, it just oozes with style.
As for your friend, I don't think it is anything to worry about. But if he starts to get too crazy with the sword, or have you call him Hellsing or something, then you should be worried.