“Hey,hey”. That’s how I greet the horses every morning. I’m not much
of a “hey, you” kind of girl but it it fits for horses because of how it sounds. Playing with words is probably natural to writers. And when I find I’m doing it, it makes me smile. It can make readers smile, too, or roll their eyes. So where do you draw then line?

• Style:
  It is all in your style. The richness of your voice, your playfulness, all set the reader up for the tongue in cheek or unusual turn of phrase.

• Character:
  When playing with words in dialogue or thought, some characters do
  it more naturally than others. If you are going to do it, you
  probably should make it a character trait and have the character
  play with words several times. One time will stand out but not
  necessarily in a good way. Make this a real trait and not just a
  behavior for laughs. What kind of character would say or think such
  a thing? A person with a certain kind of depth and certain sense of
  humor.

• Reader:
  Everything is for the reader. This does not mean that your word play
  needs to be so blatant that it is caught by every reader. It does
  mean you should remember that your reader probably will not catch a
  play of words that is an inside joke only between you and your
  friends. But they might.