What is Knock Knock?

Knock knock..
whos there?
Wendy..
Wendy who?
Wendy last time you take a bath?

Jianshuo,
It's a common western joke. I remember in the "Catch me if you can" movie Tom Hanks twisted this joke a bit. Basically here "knock knock" means somebody knocks on the door.

I remember my co-worker says "knock knock" when visiting my cubicle (trying to get my attention).

It's kind of a joke format, where the format is always the same and the only thing that changes is "X" below, the premise is someone is knocking at the door and the other person is asking who it is:

A: Knock Knock
B: Who's there
A: X
B: X Who
A: XXXXX (this is the "punchline" of the joke)

By the way, my kids think it is hilarious!

Can someone translate it to Chinese please?
Not only with Chinese characters but also in pinyin.
Just curious to know how it (aproximately) sounds in that language. ;-)

Two of my kids' favorites:

A: Knock knock
B: Who's there?
A: Who
B: Who who?
A: Is there an owl in here?
(note: "Who Who" is how we, in English, imitate the sound an owl makes)

A: Knock knock
B: Who's there?
A: Boo
B: Boo who?
A: You scared me!

Hehe... we grew up with 'knock knock'... the original version of the 'orange' one is:

A: Knock knock
B: Who's there?
A: Orange
B: Orange who?
A: Orange u glad I didn't say banana!

But I personally love this one:

A: Knock knock
B: Who's there?
A: Interrupting dog
B: Interrupting dog w....?
A: Whoof whoof!!!!

(Sounds funny when the other person is just in the middle of saying "Interrupting dog who" - so the dog interrupts) :p

@Mark - I remember the 'boo who' one as:

A: Knock knock
B: Who's there?
A: Boo
B: Boo who?
A: Oh... no need to cry!!!

Explanations for the first two:

"Orange you" sounds like "Aren't you", so "Aren't you even going to open the door?"

"Wendy" sounds like "When d'you" (when did you), so "When did you last time take a bath?"

I remember , in the movie "You have got mail", Tom Hanks also tried to use this joke to help Kathleen in the supermarket.
A: Knock knock
B: Who's there?
A: Orange
B: Orange who?
A: Orange u going to give us a break...
by zipping credit card through the credit card machine?

@ JS - don't bother if you don't understand. It's just a silly pun joke thingy played by very young kids. Usually nonsensical word play. It don't work when you translate it to chinese. I was once so hounded by my young Canadian nephew with so many knock knock "jokes" that I wanted to slap him. So I gave him this :

Knock, knock,
Who's there ?
Screw.
Screw who ?
Screw you and git lost !

王小丫与拉登的开心词典
王小丫：拉登您准备好了吗？
拉登：准备好了。
王小丫：请听题：五角大楼被炸掉一个角，还剩几个角？A：4个角B：6个角？
拉登：（毫不忧郁）四个角。
王小丫：您确定吗？您如果答对这道题，可以得到【博客无忧】为您提供的‘沙鹰’手枪一支。（展示银色手枪）
拉登：拽拽长长的胡子……
王小丫：您可以打求助电话，也可以去掉一个错误答案，或者求助现场观众。
拉登：我打求助电话。
王小丫：（拨通布什电话）喂，您好布什先生，拉登在我这里……
布什：那个sb在哪？欠他10美金就把我世贸炸了，五角大楼也给我炸一个角去了，全美国都笑我，人家是五角大楼，我是tm四角大楼……
王小丫：对不起，布什先生，这里是开心词典，拉登让我求助您。五角大楼炸掉一个角还有几个角。现在有两个备选答案A：4个角B：6个角。
请问您选则A还是选择B？
布什：（片刻忧郁）B！就是B（挂上电话心想，我tmd就不告诉他正确答案）
拉登：我也选择B，因为我相信布什应该去数过。
王小丫：您确定吗？
拉登：确定
王小丫：恭喜您，答对了！
拉登：挥舞着手中的AK-47庆贺。
王小丫：请听下一题：萨达姆是在哪里被抓住的A:树林里B：山洞里C：地洞里请选择？答对这道提您将得到【博客无忧】提供的火箭炮和10枚炮弹。
拉登：搓手，这个不好答，我当时在山洞没看见老萨，不应该是B，我要去掉一个错误答案。
（王小丫去掉答案A）
拉登：C
王小丫：确定吗？
拉登：确定！
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王小丫：拉登选择C，我们恭喜他，答对了！
拉登：再次挥舞AK-47
王小丫：由于时间关系，我们问您最后一题。布什为什么要坚持杀萨达姆？A：由于债务拖欠原因;B：一怒为红颜;C：看萨达姆长的比他帅
拉登：这个问题不好回答，一般都是布什拖欠别人钱，不会是A。萨达姆长的还不如我帅，布什应该杀我才对，不应该是C。我还是求助现场观众
（A:12%B:74%C:14%)
拉登：我选……不好，我要走了，我比萨达姆帅，萨达姆比布什帅。我怕有杀身之祸……
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这时走进几个洋鬼子：对不起我是FBI请问见过这个人吗？（拉登相片）
王小丫：刚才还在这，估计现在乘直升机去做整容了！

@wonton... ahh - only disagree with you on one point - even 'old' people like me can still get a real laugh out of 'knock knock' jokes... the more stupid and nonsensical the funnier!! - Maybe it's a culture thing? Or maybe just shows my level of immaturity... :p

@wangzi - is this your attempt at humour?

@AussiePB: Don't worry, my taste is probabily not that much ahead. I prefer silly limericks. heh heh.

There was a fella named Bates,
who could dance the fandango on skates.
But a fall on his cutlass,
rendered him nutless,
and practically useless on dates.

Knock - 敲 qiāo

Raquel