Here are some interesting facts about St. Patrick and the Irish which are sure to get you beat up in an Irish bar if you repeat them.

St. Patrick the Englishman

St. Patrick was born and raised in England.  Just mentioning this will raise the dander of at least one drunk Irishman on St. Paddy's day.  Patrick wasn't what you'd call British, he was a Celtic Briton.  Calling him British is just more fun.  Either way, he was not Irish.

If he's English how'd he get to Ireland?

St. Patrick arrived in Ireland via kidnapping.  He was kidnapped at the age of 16 by Irish raiders, and forced into slavery for six years.  After six years, God told him to get out of Dodge Dublin and return to England (he wasn't actually in Dublin, but you get the point).

Stockholm syndrome

Apparently he had so much fun with forced labor in Ireland, an angel told him God was just kidding and he needed to go back to Ireland as a missionary.  When he returned, he studied in England (or France depending on your history source) for 15 years to become a priest.  After he was ordained, his first task was to minister to the Christians living in Ireland and to convert the rest of the Irish.  Lucky him.  Returning to Ireland, he was greeted with beatings from thugs and a hostile Irish monarchy.

St. Patrick had sloppy seconds

Note his first task in Ireland included minister Christianity to the Christians already living there.  He did not introduce Christianity to Ireland.  Palladius, the first Irish bishop, was sent by Pope Celestine in 431 A.D. to minister to "the Irish who believe in Christ" before Patrick.  Any one who has ever played chess knows you send the pawns in before the bishops, so there were  missionaries in Ireland before Patrick was ever kidnapped.

St. Patrick is schizophrenic

There is more lore to St. Patrick than reality.  The truth is much of the St. Patrick persona is derived from several missionaries at the time.  Even the Irish cannot agree who St. Patrick was.  If you ask a Catholic Irishman, he'll tell you St Patrick was directed by the Pope to bring Christianity (Catholic-style) to Ireland.  If you ask a Protestant Irishman, he'll tell you St. Patrick was an Irish hero who was anti-Catholic and created a Celtic Christian church with their own symbology.   

St. Patrick isn't a saint

Ask an Irishman which Pope cannonized St. Patrick, and you'll most likely get a blank stare.  The reason is St. Patrick is not a saint.  He is not an official saint recognized by the Catholic Church.  There have been efforts to make him a saint as recent as John Paul II, but none have recognized the man as a saint.  The reason is there is too much myth surrounding the man.  It is hard to determine what he did, what others did but attribute to St. Patrick, and the stuff that was made up after too many pints of stout.  To be a saint, he needs three verifiable miracles.  The only miracle anyone attributes to him is removing the snakes from Ireland.

Ireland never had snakes

When St. Patrick drove the snakes from Ireland, apparently he drove all snake fossils out of the country too.  No scientific evidence has ever been found showing snakes ever existed in Ireland. 

If snakes ever did exist on Ireland, the ice age most likely drove the snakes away.  Ireland was blanketed with ice 15,000 years ago, and the island hasn't had a land bridge to England since.  Snakes cannot travel across icy oceans, and Ireland has 12 miles of icy water seperating them from England.  Other islands do not have snakes.  New Zealand and Hawaii also do not have snakes, as well as many other smaller islands.   

Here are a few bonus items to get you beat up if the above items do not work.

Irish have more babies outside of Ireland

Thirty-six and a half million people in the United States claim they are Irish.  This number is almost nine times the population of Ireland (population of Ireland is 4,156,119).  Most of these people have never set foot in Ireland.

Notre Dame is not in Ireland

It's in France.  Every child who has seen the Hunchback of Notre Dame knows this. 

Most colleges at the turn of the last century were formed by different religions.  There were Methodist schools (Southern Methodist), Mormon schools (Brigham Young), and there were Catholic schools.  Notre Dame was founded in 1844 by Catholic missionaries (not Irish).  They are known as the Irish because the school was known as a Catholic school, and many Americans associated Catholic with Irish.  The "Fighting Irish" name for the football team originated the 1920s by alumnus Francis Wallace in his New York Daily News columns.

If all else fails, wear orange

Orange is the color of Protestant Irish and gets it's roots from William of Orange.  The Protestant Irish and the Catholic Irish don't really play well together.  They have been bickering (read "blowing up each other with bombs and such") since the 1200s.  Wearing orange in an Irish bar is like wearing red at the running of the bulls.  It makes you a great big target.

So why celebrate?

The real reason most people celebrate St. Patrick's day is because it's fun to get drunk.  Not so much fun the next day, but that is tomorrow's worry.  So raise a pint to the myth and enjoy the evening.  Best of luck to you, and Erin Go Bra-less!!