i'll end up with the whole fucking human race in it if i don't watch out.
I believe he must be in charge of getting actors for a play. He says Christ, what a character. Wish there were a place for him in the play. So, what he means is he cannot put this person in the play because there really isn´t a place for him. If he is not careful, he will have too many actors - that is, he would put the entire human race in the play if he is not careful. His concern is having too many actors in the play.