The Irish don’t celebrate Fat Tuesday, they celebrate Pancake Tuesday. An Irish boy told me this harks from way back when (when exactly, I don’t know) they would give up sugar and milk and eggs for Lent, so they would use up the last of it making pancakes the day before Ash Wednesday. (The validity and/or accuracy of this explanation may be undermined by the fact that he was rather intoxicated at the time.)
However, I am still a huge fan of this tradition. What they call pancakes are actually crepes with sugar and lemon juice. And they don’t like it when you call crepes [krAYps]. But they are delicious, and our neighbors made them for dinner. In turn, we made American biscuits (biscuits to them are cookies). They insisted that these biscuits were just scones, and I failed to give the difference between biscuits and scones.