Call him 'Little Shit' until he gives up.

As long as you are now on an equal basis, then make it equal all the way. Tell him now that you are equals he pays rent and for anything else he gets (food, car, etc.). And no more allowance, now that he is a big independent guy.

Start charging rent since he doesn’t want to treat you like his parent anymore

Call him by an embarrassing nickname that you used to call him when he was a baby every time he does that.

Me: “Mr Anderson surprised to see me?” My dad: “No.” Me: “Then your aware of it?” My dad: “Of what?” Me: “Our connection. Our connection. I don't fully understand how it happened, perhaps some part of you imprinted onto me, something overwritten or copied. it is at this point irrelevant, what matters is that whatever happened, happened for a reason...” My dad .... 😩

Let him but his own car and health insurance. He’ll be calling you Daddy in no time!

Next time he needs something, tell him he should ask his dad.

Start calling him "bro" or "dude"...whenever he asks for something you say out loud "Lol, homey!" or " You so gangstaaaa". (Nice side effect if it doesn't help: You have a bro, homey, dude from now on! No need to go outside to hang out with your fav gangsta dude! You so rad now!)

Where's the FML?

So start calling him your tenant and make him pay rent.