Knock knock.
Who’s there?
To who?
No, “to whom.”
When I told the people of Northern Ireland that I was an atheist, a woman in the audience stood up and said, 'Yes, but is it the God of the Catholics or the God of the Protestants in whom you don't believe? -- Quentin Crisp
To whom did the squirrel go to seek out his fortune.
Whom did the cheesy Bible start with? Edam and Eve.
Knock knock
Who's there?
To who?
Surely you mean to whom.