Perhaps there is additional motivation to celebrate St. Patrick's Day for people like me who were born with an uncertain mix of Scandinavian and Celtic DNA: a sense of duty even, or... is it a sense of appeasement? After all, those Viking seafarers were mighty attracted to the comely lasses along the Irish coast. Recent DNA research has shown that a large portion of Icelanders are in large part Irish, resulting from all the "Maggie Reds" who were courted, convinced, or outright abducted, and then found themselves serving up grog and cod to their Viking mates on a foreign shore. Then, oh dear, there is the incident concerning some modern-day "Vikings" who sailed into Dublin Harbor during the summer of 2007, boldly intent on apologizing to the Irish for their bad behavior of over ten centuries ago. Better late than never, I suppose.  
I went for a walk along the quays, along the quays, along the quays
Diggers and shovels and J.C.B.'s were digging up the Vikings
Digging it up and pulling it down
Pulling it down, pulling it down
Digging it up and pulling it down, poor old Dublin town
A Viking came to Dublin town, Dublin town, Dublin town
Took one look and he turned around and sailed back home again
They were ripping it up and tearing down
Tearing down, tearing down
They were ripping it up and tearing down 
Luci's papa claims to be a "Heinz 57" variety, but will say he is Irish when pushed. She has documented her father's roots back to Ireland, where his fifth great-grandfather came from Stweartwtwon in Tryoe County. After the age of five, Luci grew up in St. Paul, Minnesota, where the Irish are known to have played an itegral part in the city's founding and growth. St. Paul held Minnesota's first St. Patrick's Day parade in 1851--an impromptu event with participants partaking in flag-raising, speeches, and a fired salute. The Irish were every bit as attached to their homeland as the Norwegians, it seems, but a bit more demonstrative about it. 
My mother, who was born in Minnesota, but whose family is full-blooded Norwegian on both her mother's and father's side, celebrates her birthday on St. Patrick's Day. For as long as I can remember, her birthday cards and gift wrapping have not reflected her Scandinavian background, but were more likely to have been studded with clover leaves, leprechauns, and green, green, and more green. As for me, my non-Norwegian side leans more toward Scotland, as far as I can tell, but since I am not really certain what my ancestors have been up to, I always play it safe and participate in the "wearing of the green" each March 17th.
To quote an Irish toast:
If you’re enough lucky to be Irish...
You’re lucky enough!
You’re lucky enough!
 The story of St. Patrick
 Largest to Date Genetic Snapshot of Iceland 1,000 Years Ago Completed
 Viking Apology 1,000 Years in the Making
 Lyrics excerpt: Lynch, Bob. From the Land of the Carolan, CBS, 84268, LP (1980)
 Wikipedia: The History of the Irish in St. Paul
Image sources: Vintage Holiday Crafts and Karen's Whimsy