Spoonerisms are phrases, sentences, or words in language with swapped sounds. Usually this happens by accident, particularly if you're speaking fast. Come and wook out of the lindow is an example.

Of course, there are many millions of possible Spoonerisms, but those which are of most interest (mainly for their amusement value) are the ones in which the Spoonerism makes sense as well as the original phrase. Go and shake a tower and a well-boiled icicle illustrate this well (go and take a shower, a well-oiled bicycle).