All players are in a circle with drinks. The leader says the line "One fat hen." All players repeat in turn.The leader repeats the first line, adding a second: "A couple of ducks." All players follow suit. A new line is added each round, and whoever fucks up has to drink and say the whole rhyme from the beginning to that point. Here are all of the lines:

One fat hen
A couple of ducks
Three brown bears
Four fast hares
Five fat females
Six simple Simons sitting on a fence
Seven stupid Sallys collecting sea shells by the sea shore
Eight elongated alligators elevated in an elevator
Nine nude nymphomaniacs kneeling near a nook
Ten two-ton tractor trailers towing tasty tomatoes to Tijuana tonight