Não é uma piada, é um trava-língua, mas as tentativas de pronunciá-lo acabam sendo engraçadas.
Betty Botter bought a bit of butter.
The butter Betty Botter bought was a bit bitter
And made her batter bitter.
But a bit of better butter
Makes better batter.
So Betty Botter bought a bit of better butter,
Making Betty Botter's bitter batter better.