“Can you enter a house uninvited?""No.""Why?""That would be rude.”
“That would have been the worst kind of violation, to read you words uninvited.”
“Professor, why couldn't we just Apparate directly into your old colleague's house?''Because it would be quite as rude as kicking down the front door,' said Dumbledore. 'Courtesy dictates that we offer fellow wizards the opportunity of denying us entry.”
“Waking up to a smell is a lot more satisfying than waking up to a noise. Instead of barging in uninvited and yanking you out into reality, smells enter your dreams with a silent knock and a polite "Excuse me?”
“And what would you do, if an uninvited dwarf came and hung his things up in your hall without a word of explanation?”
“When you least expect to recall something, a memory can pop up like an uninvited guest on your doorstep.”