A classic Mother Goose nursery rhyme
which has inspired many other uses for the name. The best known verses (there are others):
Simple Simon met a pieman going to the fair;
Said Simple Simon to the pieman, "Let me taste your ware,"
Said the pieman to Simple Simon, "Show me first your penny,"
Said Simple Simon to the pieman, "Sir, I have not any!"
Simple Simon went a-fishing for to catch a whale;
All the water he had got was in his mother's pail.
Simple Simon went to look if plums grew on a thistle;
He pricked his fingers very much which made poor Simon whistle.
He went to catch a dicky bird, and thought he could not fail,
Because he had a little salt, to put upon its tail.
He went for water in a sieve but soon it all fell through;
And now poor Simple Simon bids you all "Adieu."
In 1930, Katherine Elwes Thomas argued in The Real Personages of Mother Goose that "Simon" here was a reference to King James I of England, who sold royal honors and titles for money for his treasury. Peter and Iona Opie discredited this idea in The Oxford Dictionary of Nursery Rhymes in 1951.
There is an 1855 Hans Christian Andersen story about a character named Simple Simon in some versions but most commonly "Jack the Dullard" (as well as Clod Hans, Clod-poll, Clumsy Hans and Numbskull Jack). In this story, Simon/Jack is a supposedly stupid youngest son who manages to win the princess's hand in marriage where his two older and supposedly smarter brothers have failed. Under the name of "Simple Simon," a script version for toy theater was written by Alfred Jacobsen in 1928.
A ballad published in chapbook form in the late 1600s called "Simple Simon's Misfortune" (among other versions of the title) and retold in prose later, chronicles a man called Simon who seems to lose and break things and his wife Margery's cruelty to him throughout their marriage. This was so popular that in 1889 The Reader's Handbook of Allusions, References, Plots and Stories by Ebenezer Cobham Brewer still defined "Simple Simon" as "a man more sinned against than sinning, whose misfortunes arose from his wife Margery’s cruelty, which began the very morning of their marriage."
Because of all these old usages, to call someone a simple Simon usually means they aren't very smart, or at best, that they are quite naive. Harriet S. Morgridge's 19th-century sonnet retelling casts the original rhyme protagonist's character differently:
A boy named Simon sojourned in a dale;
Some said that he was simple, but I ’m sure
That he was nothing less than simon pure;
They thought him so because, forsooth, a whale
He tried to catch in Mother’s water-pail.
Ah! little boy, timid, composed, demure,—
He had imagination. Yet endure
Defeat he could, for he of course did fail.
But there are Simons of a larger growth,
Who, too, in shallow waters fish for whales,
And when they fail they are “unfortunate.”
If the small boy is simple, then are both,
And the big Simon more, who often rails
At what he calls ill luck or unkind fate.
There is a 1935 animated short movie based on the nursery rhyme, and a 1922 silent movie described by the IMDB as a romance (thus probably not based on the poem). Simple Simon is also the title of a 1996 novel by Ryne Douglas Pearson about "a 16-year-old autistic genius being protected by a renegade FBI operative against a secret government agency"; this book was made into the 1998 movie Mercury Rising.
There was also a 1930 musical called Simon Says, with music by Richard Rodgers, lyrics by Lorenz Hart, and book by Ed Wynn and Guy Bolton. It starred Ed Wynn as a Coney Island newspaper vendor whose fantasies send him to fairy-tale lands where bad news doesn't exist. The musical contained the song "Ten Cents A Dance," sung by Ruth Etting, which has a #5 hit in 1930.
"Simple Simon" is also the name of a variation of solitaire. However, the game of "Simon Says" does not traditionally have anything to do with "Simple Simon" -- the bubblegum band 1910 Fruitgum Company's 1968 song "Simon Says" seems to be the oldest thing I can find that combines the two, saying "The name of the game is Simple Simon says."
Given the references in the best-known first verse of the rhyme to pies, it's not surprising that there are Canadian (www.simplesimonpies.com), Scottish (www.simplesimonspies.co.uk) and South African (www.simplesimonpies.co.za) pie makers who've used the name, as well as an Australian manufacturer of pie-making equipment (www.simplesimon.co.au) and American pizza pie franchise (www.simplesimonspizza.com), as well as several restaurants and pubs. The reason the name is used by a company (www.simplesimon.com) that "provides cutting edge computer telephony solutions for businesses and individuals" is not nearly as obvious to me -- I suppose "simple" is meant to imply that their computer software is easy to use.
And Simple Simon was also the name of a 1990s 3-piece hard rock band from Chicago who released four albums and one EP on Kentland Records. Their record label's site describes them as now "on semi-permanent hiatus."