For example,
A piece of string walks into a bar and orders a beer. "I'm sorry, we
don't serve strings," says the barman. The piece of string goes away,
unravels its ends, ties itself into a figure-eight, and returns. The
barman peers at it curiously. "Are you sure you're not a piece of
string?" he asks. "No," says the string, "I'm afraid not."
-- Gareth Rees