My 5 year old told me today that he would rather be a stuffed animal than a boy because then he'd never have to die. I said but then he'd never feel the love of his family or eat ice cream or experience all the other wonderful things in life. He then went in to deny he liked ice cream, so I'm not sure how he processed that.
I do think GT kids may think about these things more/differently/earlier, but I do think it is usually normal.