My boss,

Charlie (confident): ' i thought about calling hot line to sing you happy birthday'.
me(bewildered): 'But you don't sing'.
Charlie (still confident): 'I know. Would you be embarrassed if I had?'
me (increasing bewildered): 'why would I be embarrassed, you are the one that doesn't sing.'
Charlie (very proudly): 'I don't even hum'.
me (becoming greatly amused): 'or whistle'.
Charlie (even prouder, if that is possible): 'yeah, I can't'.
me: 'can't what'.
Charlie: 'whistle'.