It is supposedly Spoonerism Day, at least in the USA. By way of note, the USA has many such acknowledgment days almost every day. For example: today is also National Penuche Day, Mango Day, and Lion’s Share Day.
If you don't know about Spooner, this is what Wikipedia has to say.
William Archibald Spooner (22 July 1844 – 29 August 1930) was a long-serving Oxford don. He was most notable for his absent-mindedness, and for supposedly mixing up the syllables in a spoken phrase, with unintentionally comic effect. Such phrases became known as spoonerisms, and are often used humorously. Many spoonerisms have been invented and attributed to Spooner.
The Spoonerism Day website, lists spoonerisms that he might have uttered.
It is kisstomary to cuss the bride."
Blushing crow" (crushing blow).
The Lord is a shoving leopard" (Loving shepherd).
A well-boiled icicle" (well-oiled bicycle).
I have in my bosom a half-warmed fish" (half-formed wish—it is believed he said this in a speech Queen Victoria).
A toast to our queer old dean" (our dear old Queen).
Will nobody pat my hiccup?" (Will nobody pick my hat up?)
Go and shake a tower" (Go and take a shower).
Is the bean dizzy?" (while hoping to speak to a college dean).
Mardon me padom, you are occupewing my pie. May I sew you to another sheet?"