For some reason, everybody used to make fun of the Irish. I won't delve too deeply into the why's and how's of that. It's a bit complex and it would take me forever to type with my thumbs. A feller named Christie Davies has written a good bit about ethnic humor if you'd like to know more.
Nowadays Irish jokes mostly deal with drinking (which might have something to do with St. Patrick's day), but most Irish jokes used to be what folklorists call "numskull" jokes. The main characters in this country are Pat and Mike and most of the old anecdotes paint them as unbelievably ignorant immigrants. Fresh off the boat, they talk funny, and just don't understand anything about their new home.
These jokes were spread around different ways, via vaudeville, minstrel shows, joke collections, newspapers, and of course, word of mouth, and the Irish themselves. Geo Evans' 1859 book of anecdotes (on kindle, free) is loaded with them, Joe Miller's Jest book from the 1700's even has Irish jokes. Irish ethnic humor in this country most likely stemmed from the flood of Irish to this country at the beginning of the 1800's.
Anyways, we have Irish Jokes in the WNC mountains too where they ain't a lot of Irish-Irish (Scots-Irish does not equal Irish). Most of them follow the numskull formula, but some people even say "uncle Pat and uncle Mike" which is interesting. The best jokes, like the one below, actually manage to turn the joke around on "us." I learned this one from Ray, who got it from his father, born in the 1800s. A good number of Ray's ancestors game to this country via Ireland, like the Coffeys and the Graggs.
Pat and Mike Come Upon a Baptizing
Well pat and mike were going through the country, and they come up on a creek baptizing. By this time they had been in the United States long enough that it wasn't the first time they had seen one. This skinny little preacher was leading in this big heavyset woman, and when he went to lean her back her foot slipped and his did too and they both went under. When they come back up, the preacher just happened to be a-stradle her back. Pat turned to Mike and said "Faith in me Christ! I've heard of leading em in and leading em out, but here they lead them in and RIDE em out!"
Another Irish joke I particularly like came from a church bulletin!
The Irishman Gets Baptized
An Irishman went out on a bender and woke up the next morning at the foot of a tree. He heard the most beautiful singing he'd ever heard in his life. So he followed it. He came to a river where a crowd of people were being baptized, and finally the preacher sees the Irishman and motions him over. The Irishman staggers over and the preacher grabs him by the collar, looks him in the eye and says,
"Son, are you ready to find Jesus!"
And, the Irishman says,
"I reckon I am?"
The preacher plunges him under and pulls him up.
"Son, did you FIND Jesus?"
"No, hant found him."
Again the preacher plunges him down.
"Son, did you FIND Jesus?!"
"NO, Han't found him!."
A third time the preacher plunges him in and holds him under for a long time, and pulls the Irishman up--sputtering and coughing.
"NOW SON, TELL ME NOW, DID YOU FIND JESUS!?!"
"NO!! *cough* *sputter* Are you sure that's where he FELL IN??"