My dad enjoyed this joke [from many years ago]:

A poor farmer worked long and hard to send his eldest son to college. He looked forward to saying with pride that the family finally had their first college graduate. Son grew up, went off to college. His father continued working hard to pay the tuition.

Four years later, son came home with a diploma. Excited to know what the son had learned, his father asked him to tell him something.

Son replied "Pi r2," which the father heard as "pie are square."

Shocked and angered, the poor old father tore his straw hat off his head in disgust, threw it onto the ground and yelled at his son: "You dingbat! Pie are ROUND...cornbread's square!"