A reader named Karen (thanks Karen!) enlightened me as to the existence of a fornicating deer motif pattern on Ravelry. It was designed by Anne Rutten, and is available as a free download here. It has really added considerably to the joy of my holidays to see that, as of this writing, the motif has or is being used in 1380 projects on Ravelry. Most of the projects are hats, but there are also socks, scarves, and a few sweaters. Here are a few pictures.
If you don't celebrate Christmas but procreating animals are your thing, you might want to check out some of the other naughty animal motifs on Ravelry: there are cows (for the Black Angus farmer convention), kangaroos (for that trip to Australia), elephants (for that relative in Africa), penguins (for that expedition to the South Pole), bunnies (for Easter), and unicorns (for that friend of yours who really likes unicorns).