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Waiter: "It's Bean Soup sir"
Customer (annoyed): "I don't care what it's been; I want to know what it is now".
Explanation of why the above Bean Soup joke is the funniest Bean Soup joke known:
Been is the past participle of To Be, and is pronounced the same as bean (the vegetable).
The customer thinks the waiter is using the present perfect tense and saying, “It has been soup”.In other words, it was soup in the past, but it is something different now. The customer wants to know what it is in the present tense.
What the waiter is really saying, however, is that “It is bean soup”, and not "It has been soup" (note the different spellings).
But the joke is also funny on different levels:
The customer is puzzled as to why the waiter is telling him what the food has been in the past. This suggests that it was soup that has been rejected by a previous customer and is now being p*ssed off as something else just to gett*en rid of it. "It has been soup" infers that it was soup once but it is something else now.
The customer is obviously annoyed about this so he asks the waiter what the soup has been converted to "I want to know what it is now". This also supposes that the waiter has accidentally admitted that the food was previously soup and has now been converted to something else; which in itself is a very humourous mistake for the waiter to manufacture. :natter:
If a customer asks what food the waiter has brought, why would the waiter tell them what the food had been in the past? He wouldn't of course (excuse the pun) and this is yet another level of very funny humour to be enjoyed.
Is there any wonder that this Bean Soup joke is not just the best Bean Soup joke, but probably the best joke of all time.
Whatever next ? 
Is that better? 