Dealing with someone delusional

We've all been there. You deal with someone who acts and thinks like they are more than what they really are. Almost delusional, but in a very deliberate way. This person tends to fraternize with you, thinks they are "one of you" but in reality they come across as a try hard and unoriginal. I hate to be the guy who tells someone off or slaps them in the face with reality, but are these people just walking around living their lives thinking and behaving like this? I feel like if someone doesn't put this sort of person in their place, they'll continue to live in their delusional world. What's the best way to have these people reflect and understand they aren't who they think they are?  (Yes, I am aware of cognitive biases and personal perception but I'm talking about OBVIOUS delusional - just not who you are - but acting like you are, people)

Will refuse to list off my standards for what constitutes being "more" etc. but I think the overall concept makes sense as we have all dealt with a person who is like this at least once in our lives.