how about “i’m poopin' here” in a Brooklyn accent?

Any of those responses would be absolutely fine, I don't know how this became a "funny talking point" lately. Just say any of that.

"Occupado!" or "Oi!"

Ask "Who's there?" lmao

Just a minute is my go to

I thought everyone else also said what I say: “busy!” Or “I’m busy”

this reminds me of a John Mulaney bit

That's why you say someone

“HEY! I’M POOPIN’ EERE!”

We can’t share the toilet

“You don’t wanna come in here!” 💩