I See Your Point

(Earlier in the day Frank heard his grandson say into the phone “don’t let your mouth write a check that your butt can’t cash.” Frank likes that! He’s going to use it. Later, while sitting in the park with his friend Sam, Frank tries to use the phrase. But he hasn’t gotten it quite right.)
Sam
They keep sending me gloves, calendars, birthday cards. They’re always asking for money.
Frank
Don’t cash a check with your butt.
(Sam turns, bewildered.)
Sam
What did you say to me?
Frank
I said ‘don’t cash a check with your butt’.
Sam
Why would you say something like that to me? What does it mean? My BUTT?
Frank
I think you’re in over your head. That’s all it means.
Sam
I’m gonna have to remember that.
‘Don’t cash a check with your butt’.
Frank
(reflecting) Maybe it’s ‘don’t let your butt write a check. don’t let your butt write a check? don’t let your butt write a check.’
Sam
Stop saying that! Now all I can picture is someone with a pen sticking out of their butt, trying to write a check!
Frank
I think that’s what my grandson meant. Don’t write checks with your ass. That makes sense, right?
Sam
(thinks about it a moment)
Of course.
Frank
Yeah. Don’t write a check with your butt. No. Don’t LET YOUR BUTT write a check.
Sam
Don’t let your butt write a check. It means…?
Frank
It means you’re in over your head. Don’t let your butt write a check, you’re in over your head.
Sam
Don’t let your butt write a check, you’re in over your head.
Frank
That’s right.
Sam
Like I need another calendar.