Traditionally, all pitchers or buckets were empty except for one. No one knew who was going to get baptized. BIG surprise.

one song leader to another, with a story about they great joke they heard, often telling a real joke first that the hearer doesn't care for

Knock Knock …
Who’s There?
Put …
Put Who ?

Put up a billboard up on the hill
Those crazy billboards gave me such a thrill
When I was younger, and but a child
Those crazy billbards drove me wiiiiild, hey!

This is the last joke
Knock Knock, Who’s there?
John, John who?
JOHN THE BAPTIST! dump the water on crowd member(s)