What's ALSO tricky is: How do you refer to a character while they're
1) using an alias or disguise (George, but everyone thinks he's Samantha for 30 pages) or
2) your character George, who is regularly possessed by and is controlled by ... the spirit of the dead Samantha
How would you do those, do you think?
GEORGE (as Samantha)
... or something like that?
What you generally need to be guided by in that situation is -- what does the audience know/believe?
If the audience believes that a character is Samantha, then you should introduce the character as SAMANTHA and whoever it is should just be Samantha.
If there's another character - George, who everybody thinks is a different character, then introduce him as a separate character GEORGE, and give him his own name, his own identity, etc.
Now, if at some point, Samantha pulls off her wig and - surprise, it's George.
Well, then, it's going to be a surprise for the people reading the script the same way it's a surprise for people watching the movie.
From the moment of the reveal, if we now know that it's George, then Samantha disappears, and it's just George.
Now, if we're supposed to know -- you've got some choices. You could simply say, George puts on his Samantha disguise -- and then simply use "Samantha" in quotes when he's being Samantha. I think that's a lot easier than doing SAMANTHA (GEORGE) every time you reference the character, although that definitely makes it clear, and there's something to be said for always making it clear who's who.
NMS