As luck (of the Irish) would have it, I found a Village Voice article titled, "Dual to the Death" from 1999 that defines the "City Hall..." remark, and here is a copy-and-paste of the first few paragraphs:
"It is customary in my family on St. Patrick's Day to ask every Irish person you meet if he's been to City Hall yet. When someone asks why, you tell him, "To get your ass painted green."
"This is a gentle but firm reminder to never stray into the precincts of one of the more odious ethnic stereotypes: the "professional" Irishman. Sometimes referred to as the "stage" Irishman, this is a poor sod who is nearly drowning in nostalgia and will, at the drop of a plastic green derby, start in with the usual 75 varieties of horseBLEEP about the place, people and culture."
"Slobbering on about dear Erin, the sunsets and rainbows, salmon jumping through the mist, dark Rosaleen, maidens dancing at the crossroads and all the rest of the flapjaw too ra loo ra loo ra. Best to ignore him, feel compassion. But, if he tells you that St. Patrick drove the snakes out of Ireland, say, yes, he did indeed, and they all swam to New York and joined the police force."
To read the full article, here is the link: