One night a guy takes his girlfriend home. As they are about to kiss each other goodnight, the guy starts feeling a little horny. With an air of confidence, he leans with his hand against the wall and, smiling, he says to her:

"Darling, would you give me a b---j--?"
Horrified, she replies "Are you mad? My parents will see us!"
Him: "Oh come on! Who's gonna see us at this hour?"
Her: "No, please. Can you imagine if we get caught?"
Him: "Oh come on! There's nobody around, they're all sleeping!"
Her: "No way. It's just too risky!"
Him (horny as hell): "Oh please, please, I love you so much?!?"
Her: "No, no, and no. I love you too, but I just can't!"
Him: "Oh yes you can. Please?"
Her: "No, no. I just can't"
Him: "I beg you ... "

Out of the blue, the light on the stairs goes on, and the girl's sister shows up in her pajamas, hair disheveled, and in a sleepy voice she says:
"Mom says to go ahead and give him a b---j--. Otherwise I can do it. Or if need be, Mom says she can come down herself and do it. But for god's sake tell him to take his hand off the intercom..."