A popular St. Patrick’s Day riddle is:

Q: How can you tell if an Irishman is having a good time?
A: He’s Dublin (doubling) over with laughter!

The joke has been cited in print since at least 1996.


Kith and Kin (Marshfield Area Genealogy Group, Marshfield, WI)
March/April 1996
Pg. 5:
HOW IRISH ARE YOU?
TEST YOUR I. Q. (IRISH QUOTIENT)
(...)
4. How can you tell if an Irishman is having a good time?
Answers:
4. He’s Dublin over with laughter.

Google Groups: alt.humor.puns
Irish jokes - good ones please!
James D. Davis
3/2/97
Brian Carling AF4K/G3XLQ (_SPAM) wrote:
: x-no-archive: yes
:
: Hey Paddy! Would you hold these three horses while I count them?!

That had me Dublin over with laughter.

Google Groups: alt.ascii-art
Belated St Patricks Day (jgs work)
ed...@cc.curtin.edu.au
3/18/97
(...)
4.  How can you tell if an Irishman is having a good time?
(...)
4.  He’s Dublin over with laughter.

Google Books
Let’s Celebrate St. Patrick’s Day
By Peter Roop and Connie Roop
Illustrated by Gwen Connelly
Brookfield, CT: The Millbrook Press, Inc.
2003
Pg. ?:
How can you tell if an Irishman is having a good time?
He’s Dublin over with laughter

16 March 2003, Toronto (ON) Star, pg. D16:
How can you tell if an Irishman is having fun?
(he’s Dublin over with laughter)

18 March 2004, Charleston (WV) Gazette, “Touch of Life: Toasting the Irish on St. Patrick’s Day” by Don Springer, pg. 2:
Q. How can you tell if an Irishman is having a good time?
A. He’s Dublin over with laughter!

Google Groups: alt.humor.jewish
Jest For Kids Weakly 03-16-04
Stan Kegel
3/21/04
(...)
How can you tell if an Irishman is having a good time?
He’s Dublin over with laughter! (Candy Silver)

Twitter
Tom Cahillane‏
@dmcscorp
Q: How can you tell if an Irishman is having a good time?
A: He’s Dublin over with laughter!
http://www.alcoholichumor.com
7:04 PM - 9 Mar 2009

HubPages
St Patricks Day Jokes and Riddles For Kids
Updated on March 26, 2012
(...)
How can you tell if an Irishman is having a good time?
He’s Dublin over with laughter!

Google Books
Readers Digest Funny Family Jokes:
Something for Everyone from Age 9 to 99
By Editors at Reader’s Digest
New York, NY: Simon & Schuster
2014
Pg. ?:
How can you tell if a leprechaun is having a good time?
He is Dublin over with laughter!

Google Books
St Patrick’s Day Jokes
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
How can you tell if an Irishman is having a good time?
He’s Dublin over with laughter!