What? No mention of the classic Henway.
What's a Henway you may ask?
About a Kilo or 2 pounds for the Imperialists among you

Reminds me of a similar joke (don't know whether this will make sense outside the UK though given the joke revolves around British slang):
"I'm going to my sister's hen do this weekend."
"What's a hen do?"
"Lay eggs."
Here's another joke (an old one) having to do with the incompatibility of American and British slang and the untranslatability of puns:
An American is showing off his backyard vegetable garden to a British visitor, who asks what the American does with all the produce.
"We eat what we can, and what we can't, we can!"
... to which the British visitor draws a polite blank, not getting the pun.
"Well, I mean ..." the American begins to explain, but changes course: "Look, what do you do with the produce from YOUR backyard garden?"
To which the Brit replies:
"Why, we consume what we are able, and tin the balance!"