Lena was in bed with her lover, Sven, when she heard Ole's key in the door.
"Stay where you are," she said. "He's so drunk he won't even notice you're in bed with me."
Sure enough, Ole lurched into bed none the wiser, but a few minutes later, through a drunken haze, he saw six feet sticking out at the end of the bed. He turned to Lena and said, "Hey, der are six feet in dis bed! Der shud only be four. What's going on?!?"
"Nonsense," said Lena, "You're so drunk you miscounted. Get out of bed and try again. You can see better from over there."
Ole climbed out of bed and counted. "One, too, tree, four. Damn, you're right!"