A spoonerism is a slip of the tongue whereby you get the first sounds of two words mixed up, and sometimes with great comedy value!
Here are some examples:
The acrobats displayed some cunning stunts.
Sir, you are certainly a shining wit.
He fills her soul with hope.
It's the Tale of Two Cities.
Have you brought your sleeping bag?
She is sure pretty.
Have you seen her sick duck?
Oh, the suffering of purgery on my soul!
He's not a pheasant plucker.
She showed me her tool kits.
He's a smart fella.
A hot pie would make me happy.