Actually, I believe it refers to the person's toes, rather than the feet themselves.
It is a reference to the old nursery rhyme This Little Piggy, which is typically done while playing with each of the child's toes in turn.

I've seen a Looney Tune cartoon or two where it is used in this sense, and the given Wikipedia link mentions several. Most often a cartoon character almost falls off something, is hanging on by his toes, and the protagonist evilly plays "this little piggy" while pulling up the toes one-by-one.
The day "Company X"(I heard it as "Microsoft")makes a product that doesn't suck is the day they start making vacuum cleaners– T.E.D. Oct 4 '11 at 22:53