Spoonerisms

We were highly entertained by "The Muppet Frog Prince" when it first came out on CBC in 1971.
After that the tall guy in our high school with the long hair was nicknamed "Sweetums"
and the nerds among us puzzled over the wordplay in the script like
"weevil itch"   (evil witch)
by mirthday's do-tay" (my birthday's today)
"bake the hall in the candle of her brain"  (break the ball in the handle of her cane)

Now I know that this kind wordplay is Spoonerisms,
which are words with first letters transposed.
They are named for Reverend W. A. Spooner who was prone to these slips.

The best spoonerisms juxtapose two meanings which the mind grasps at the same time.  The Capitol Steps has a segment called "Lirty Dies" which tells stories from politics using spoonerisms like
"crunch of books" (bunch of crooks)

Sometimes spoonerisms are used to tone down the intensity of a vulgarity such as "bass ackwards"

The old TV show Hee-Haw used to tell the story of Rindercella
who had two sad blisters (bad sisters) , and at the end of the story "slopped her dripper" (dropped her slipper)  My Uncle Con told this story at every social event I can remember during my teen years.

It's worth noting that spoonerisms are popular and entertaining in other languages as well