Knock-knock joke

It is a roleplay exercise, with a protagonist (the punster) and an antagonist (the recipient of wit). Developmental psychologists study knock-knock joke usage in younger children as it provides valuable insight into how children advance their language skills.

The standard format has five lines:

1. The punster: knock-knock (indicating a door has been struck to gain attention)
2. The recipient: Who's there? (an enquiry)
3. The punster: a response, usually involving a name (to set up the pun),
4. The recipient: repeat the response, adding who? -- a request for clarification
5. The punster: the punch line, which inevitably involves a punnish misusage of the word set up during the response.

Some examples:

Knock knock
Who's there?
Keith
Keith who?
Keith me, my thweet printh
(Kiss me, my sweet prince)

Knock knock
Who's there?
José
José who?
José can you see by the dawn's early light?
(Oh say, can you see by the dawn's early light? -- from US's national anthem.)

Knock-knock jokes occasionally employ a pun on a common noun.

Knock knock
Who's there?
Orange.
Orange who?
Orange you going to open the door?
(Aren't you going to open the door?)

A twist on the genre, which was very famous in British school playgrounds for a time (variations omitted lines in square brackets):

Knock knock
Who's there?
[Doctor]
[Doctor Who?]
You've just said it. It's Doctor Who.

Widespread knowledge of the knock-knock form gives rise to meta-jokes:

Will you remember me in an hour?
Yes.
Will you remember me in a day?
Yes.
Will you remember me in a week?
Yes.
Will you remember me in a month?
Yes.
Will you remember me in a year?
Yes.
I think you won't.
Yes I will.
Knock knock
Who's there?
See--you've forgotten me already.