Knock, knock!
Who’s there?
Opportunity!
That is impossible. Opportunity doesn’t come knocking twice!
Knock-knock!
Who’s there?
Abraham Lincoln.
Abraham Lincoln who?
Wait! You don’t know who Abraham Lincoln is?
Doc, Doc!
Who’s there?
A knock-knock joke with a cold.
Knock knock...
Who’s there?
Irene.
Irene who?
Irene and Irene, but no one answers...