Unless there is a real specific tell-tale sign that you are explicitly using some exact representation of an individual, then you should be safe. People don't own the light which reflects off of them, and that light has no real protections, unless it is explicitly copyrighted or gotten in privacy, without consent. You can photograph anyone in public, as all banks and gas-stations and police and new-crews and others do. You don't need explicit permissions to use those images, but anyone can attempt to raise hell if you do.
As for artistic representation which doesn't actually use the explicit images of an individual, but they represent them... There is legally nothing they can do. Just look at all the presidents parody images and memes and up-skirts shots. None of them have given permission to use any of the images and few even attempt to sue, because it is a losing battle.
Now, if you were doing something illegal, like making photo-ID's, or altering videos to make it look like a person was seriously doing something illegal, that is another can of worms that falls under other laws. But, games, in parody, as fiction... No worries, unless you piss-off the wrong person and they actually care, and have lots of powerful shady lawyers, and the judge is a deceptive celebrity-fan prick.
There is also a law that says, "in parody"... It falls under "Fair use".
Unless you are actually using the person's actual skin, body and personality, commercially, it will be a hard thing for them to actually win. People are 100% unique, but similar, as are 3D models. If it is a 2D "rendering", they have even less chance of proving any "human similarity".
Honestly, that bullshit law would stop a twin from acting, imitating the other twin. However, celebrities don't play "themselves", they are playing a "character", which is NOT a celebrity, but a fictitious work of art. However, if you are going to represent "John Doe" as "John Doe", and not the character he plays, "Bobby Redfield"... Then they literally have no case, as "Bobby Redfield", is not a celebrity, or a person with rights, and the "Celebrity", "John Doe", was playing the role of "Bobby Redfield", which includes wardrobe, makeup, mannerisms, fictitious lifestyle and other "non-human owned", potential attributes of the character.
What is it that you are attempting to do?
Are you trying to accurately represent the wholeness of some specific person, (Celebrity or not, celebrities don't truly have any real enforceable laws that any single individual has, even if they like to pretend so. It is the same law that applies to all humans. They just NOTE that it was a celebrity. Not the same as a "contracted celebrity", which is another can of worms. By the way, there is no actual legally enforceable title "Celebrity", as anyone can call themselves a celebrity. By all definitions, it is a 100% subjugated perception, without any bounds.)
