Craig,
not sure where Mardi Gras fits in but Pancake Tuesday is Shrove Tuesday, the last day before Lent. Something to do with dietary restrictions and using up all the stuff in the pantry that couldn't be eaten and making pancakes out of the eggs and milk.
BTW, the very best way of eating pancakes is to first fry some chopped bacon in the pan until it's crispy and then pouring over your batter. Brown both sides and then serve with Dutch keuken stroop (golden syrup will do).
Try it, you'll be pleasantly suprised - they're called "spek pannekoeken" Yummy! :)
Mick