I think "If you ever leave me, I'll be sad and blue, Don't you ever leave me, I'm so in love with you.." was the lead in to a Beatles song that then went:

The birds in the trees would be sad and lonely
If they heard from the breeze that you'd left me only
They'd be sad
Don't be bad -- to me.

But I know you won't leave me, cuz you told me so
And I've no intention of letting you go.

(Whoops -- brain crashed. Any additional info slid off the memory table.)