Two little boys are sitting in the living room, watching
TV with their parents.  The mother looks over at the father
with a wink and a nod toward upstairs.

The father gets the message, and they both get up and head
towards the stairs.  The mother turns back to the two boys
and says, "We're going upstairs for a minute.  You two stay
here and watch TV, we'll be right back, ok?"

The two boys nod ok, and the parents took off upstairs. The
oldest of the two boys is old enough to know what's going
on now, and he gets up and tiptoes upstairs.  At the top of
the stairs, he peeks into his mom and dad's bedroom and shakes
his head.

He goes back downstairs to his little brother.  "Come with
me", he says.  The two little boys tiptoe up the stairs. 

Halfway up, the older brother says to the younger brother,
"Now, I want you to keep in mind, this is the same woman who
used to bust our ass for sucking our thumbs!"