I don't think it is a good idea or some idiot may freak out and decide that you are planning the assassination of that person.
however, typically it is ok to use public characters just don't use someone who is not public.
That's what I was thinking when I originally posted this question; actors, models, and porn stars.
I think if you were to "draw" them super close or "render" them, but not anything real (person, background, items, etc) it would be passible. Say if you traced a picture or so and it was visibly drawn, but with high detail. That I believe would work. Or if you were able to find a good render model from 3DCG and animated it. That would be okay. There are plenty of drawing/works related to celebs all over.
But, (even though this isn't against the rules) try not to let it be someone you know. Cause fantasies can lead to action, and I would hate to lose a brothern on some bullshit.>:) Like if you really have some sort of want to harm, seek actual help. Sorry, just have to put that out there.
Makehuman is an open source tool for generating 3d models of humans.
You could even import/export the generated mesh to blender and customize it further.