You know how there's no snakes in Ireland because Saint Patrick drove them all out, right? Well, do they let zoos in Ireland have snakes?
I honestly couldn't tell if the patron was being funny, clever, or serious - so I looked it up.
A simple web search for zoo ireland snakes produced quite a few good links, indicated that there are indeed (captive) snakes in Ireland.
An article from the Smithsonian not only goes into the St. Patrick myth, but also the natural history of Ireland and snakes, and says that there are snakes on the island in zoos and as pets.
Heck, there's also a Reptile Village Conservation Zoo in Kilkenny, complete with an anaconda.
But just to be sure, we also looked up the Dublin Zoo. They've had a Reptile House since the 1890s, which includes snakes, and they just got a new King Ratsnake in time for St. Patrick's day 2011 (pdf).
That seem to conclusively answer the question, and the patron apparently enjoyed the search. He chastised me for not wearing green, and then just sort of wandered away.