A customer comes in wearing a t-shirt with the Greek letter π surrounded by a spiral of about 100 of the known digits of the mathematical constant. It starts on the outside with 3.1415926... (etc.) and then spirals inwards to where it fades away.
Me: I like your t-shirt!
Customer: Oh! Yes, that's 'pi'.
Me: (stunned silence) I...know. I'm a math tutor.
Me: I like your t-shirt!
Customer: Oh! Yes, that's 'pi'.
Me: (stunned silence) I...know. I'm a math tutor.