Take her knickers down!

One night John takes his girlfriend home.  Whilst they are kissing each other goodnight at the front door they both start to feel really aroused.  With an air of confidence, he leans with his hand against the wall,
and smiling, he says to her, 
"Honey, can I take your knickers down?" 

Horrified, she replies, "Are you mad? My parents will see us!" 

"Oh come on! Who's going to see us at this hour?" he asks, grinning at her.

"No, please.  Can you imagine if we get caught?"

"Oh come on!  There's nobody around, they're all sleeping!"

"No way.  It's just too risky!"

"Oh please, please, I love you so much."

"No, no, and no.  I love you too, but I just can't let you!"

"Oh yes you can.  Please?"

Suddenly, the light on the stairs goes on.  The girl's sister appears at the door, undressed to her bra and knickers.  With her hair dishevelled, and with a sleepy voice, she says, "Dad says to go ahead and let John take your knickers down, or he can even take down my knickers instead.  Mum says, if need be she can come down herself, and he can do anything he likes with her knickers".

But for all our sakes tell him to take his hand off the intercom!