A road sweeper in the British TV comedy Only Fools and Horses has used one broom for 20 years, with 17 new heads and 14 new handles.
That's the Ship of Theseus puzzle, named after a mythical king whose ship Athenians kept repairing plank by plank.
Philosopher Thomas Hobbes added a twist: what if someone rebuilt a second ship from the old planks? Which is the original?