A riddle about a leprechaun’s pot—or “potty”—of gold is:
 
Q: Why do leprechauns have pots o’ gold?
A: They like to “go” first class!
   
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)
(...)
9. Why do leprechauns have pots o’ gold?
Answers:
9. They like to “go: first class.
 
Google Groups: alt.personals.ads
ST. PATRICK COMES OUT OF THE CLOSET!
Marsha Ann Folks
3/4/96
(...)
Q:  Why do Leprechauns have pots o’gold?
A:  They like to “go” first class.
     
18 March 2004, Charleston (WV) Gazette, “Touch of Life: Toasting the Irish on St. Patrick’s Day” by Don Springer, pg. 2:
Q. Why do leprechauns have pots o’ gold?
A. They like to “go” first class!
 
Twitter
stthomasblog‏
@stthomasblog
Q.  Why Do Leprechauns Have Pots O’Gold?: A. They like to “go” first class!
Ya gotta get out to Red Hook on St. Pa… http://bit.ly/bz1IaB
8:16 AM - 16 Mar 2010
 
Twitter
Max‏
@Maxamillion16
Why do leprechauns have pots o’gold? They like to “go” first class!
6:07 PM - 17 Mar 2010
 
HubPages
St Patricks Day Jokes and Riddles For Kids
BY Lela Davidson
Updated on March 26, 2012
(...)
Why do leprechauns have pots o’gold?
They like to “go” first class!
 
My Town Tutors
St. Patrick’s Day Jokes: Top 30 St. Patrick’s Day Jokes
Posted on March 12, 2014
(...)
7. Why do leprechauns have pots o’gold? …. They like to “go” first class!