Linguistic humor, Mondegreens

The term "mondegreen" was coined by Sylvia Wright in a 1954 Harper's Magazine article entitled The death of Lady Mondegreen. For more examples, see Steven Pinker, 1994, The language instinct. How the mind creates language. New York: Morrow. Chapter 6, 186.

Examples from my own experience

Perlmutter feels that sign is not so similar wrt grammar b/c it isn't necessary for communication, the formal structure falls by the waistside.
(In case you're wondering, this is not really what Perlmutter thinks at all—BES)

Other examples

The body consists of three parts - the brainium, the borax and the abominable cavity. The brainium contains the brain, the borax contains the heart and lungs, and the abominable cavity contains the bowels, of which there are five - a, e, i, o, and u.

Equator: a managerie lion running around the Earth through Africa.

Momentum: What you give a person when they are going away.

Three kinds of blood vessels are arteries, vanes and caterpillars.