Kenneth Koch (pronounced 'coke') could do a mean impersonation of William Carlos Williams. 'This is Just to Say', Williams's note asking forgiveness for eating the plums in the icebox which 'you were probably/saving/for breakfast' on the grounds that they were 'so sweet/and so cold', gets the Koch treatment in 'Variations on a Theme by William Carlos Williams':

I chopped down the house that you had been
saving to live in next summer.
I am sorry, but it was morning, and I had nothing to do
and its wooden beams were so inviting.

In the final variation, he confesses:

Last evening we went dancing and I broke your leg.
Forgive me. I was clumsy, and
I wanted you here in the wards, where I am the doctor!

LRB 3 August 2006 | PDF Download