The popular MO question "Famous mathematical quotes" has turned 
up many examples of witty, insightful, and humorous writing by
mathematicians. Yet, with a few exceptions such as Weyl's "angel of
topology," the language used in these quotes gets the message
across without fancy metaphors or what-have-you. That's probably the
style of most mathematicians.

Occasionally, however, one is surprised by unexpectedly colorful
language in a mathematics paper. If I remember correctly, a paper of 
Gerald Sacks once described a distinction as being


  as sharp as the edge of a pastrami slicer in a New York delicatessen.


Another nice one, due to Wilfred Hodges, came up on MO here.


  The reader may well feel he could have bought Corollary 10 cheaper 
  in another bazaar.


What other examples of colorful language in mathematical papers have 
you enjoyed?

I don't even know if this is intentional or not.  In his book Teichmuller theory, John Hubbard frequently references the category of Banach Analytic Manifolds.  He adheres to the convention that a category be referenced by the concatenation of the first three letters of each constituent word, making the category in question BanAnaMan.  This still cracks me up to this day.