In particular, I wonder about this because I believe most published works tend to have statements to the effect that "all characters, ... are trademarks of ..." and from what I've heard, it is not allowed to change one's name to a name that is trademarked.
So would this mean that, say, it would be illegal to try and change one's name to, say, "Spock" (as in the character from the original Star Trek), or say, "Bilbo" as in J.R.R. Tolkien's famous Hobbit? If so, though, could one modify the name so that it becomes "okay" while still bearing some resemblance to the original and, if so, how much would it take? E.g. if, instead of naming oneself "Bilbo Baggins" you tried "Bilboe Keane" (note both the spelling and surname changes), or something similar?
The country of interest is the United States.