"A spoonerism is a play on words in which corresponding consonants, vowels, or morphemes are switched (see metathesis). It is named after the Reverend William Archibald Spooner (1844–1930), Warden of New College, Oxford, who was notoriously prone to this tendency.
While spoonerisms are commonly heard as slips of the tongue resulting from unintentionally getting one's words in a tangle, they are considered a form of pun when used purposely as a play on words."
""The Lord is a shoving leopard" ("loving shepherd")
"It is kisstomary to cuss the bride" ("customary to kiss")
"Mardon me, padam, this pie is occupewed. Can I sew you to another sheet?" (Pardon me, madam, this pew is occupied. Can I show you to another seat?")
To a student: "You have hissed all my mystery lectures, and were caught fighting a liar in the quad. Having tasted two worms, you will leave by the next town drain" ("missed ... history," "lighting a fire," "wasted two terms," "down train")
To a lady at a college reception: "You'll soon be had as a matter of course" ("mad as a Hatter, of course")
"Let us glaze our asses to the queer old Dean" ("Let us raise our glasses to the dear old queen")
"We'll have the hags flung out" ("flags hung")
"a half-warmed fish" ("half-formed wish")
"Is the bean dizzy?" ("dean busy")
"Go and shake a tower" ("take a shower")
"a well-boiled icicle" ("well-oiled bicycle")
"Let us pray for our queer old dean" ("dear old Queen") "
http://en.wikipedia.org/wiki/Spoonerism
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