When the usher noticed a man stretched across three seats in the movie theatre, he walked over and whispered:
"Sorry sir, but you are allowed only one seat."
The man moaned but didn't move.
"Sir," the usher said more loudly, "if you don't move, I'll have to call the manager."
The man moaned again but stayed where he was. The usher left and returned with the manager, who, after making several requests for the man to move, called the police. The cop looked at the reclining man and said,
"All right, what's your name, joker?"
"Joe", he mumbled.
"And where are you from, Joe?"
Joe responds painfully, "The balcony!"
An usher is a person who shows people to their seats in a theatre or cinema.
If you are stretched across three seats, it means you are lying across three seats.
To moan means either to complain or to make a quiet, low sound. Here, the usher probably thinks that the quiet, low sound is made because the man is drunk.
Reclining means lying down.
Mumble means speak quietly and not very clearly.
The balcony is the second floor of a theatre or cinema. The man obviously fell from the balcony and is lying injured on the seats below.