The Duck Paradox

Of all the riddles I heard (or told) as a kid, the one I remember best is:

” What’s the difference between a duck ? ”

As some of you know, a frequent answer to this is ” One leg is both the same. ”

What makes this funny ?

Is it true  ?

What answers does one find if contemplated as a Koan ?

When using the duck question in a clown act I used to do, I often added:

So, what do you get when you find two of them ?

You have a paradox [ducks]

Googling, found a surprising quantity of references to it. One writer presents an interesting paper on questions and consciousness, which [spoiler alert] adding to the paradox, also does not answer the duck question: http://www.rogerr.com/galin/papers/duck.htm