It's been said, lovingly by some, that Scots are a bit slow on the uptake. A familiar story reminds travelers to never tell a Scot a joke on Saturday for fear he'll laugh in church on Sunday. Taily Day takes advantage of that, a day of joviality, every April 2. A day set aside for buttocks pranks and jokes. A fest which ultimately does not travel well.
The "kick me" sign is the funniest, my dour countrymen could come up with.
Should you ever wonder why Benny Hill and Monty Python were hung up on butt and flatulence jokes, blame the Scots. Everyone else does.