i have one, we were in science class, talking about space, our teacher asks what every teacher of mine had done 'how old is the universe?' nobody wanted to answer because we all felt we shouldn't have to answer something that useless, like answering 'whats 2+2', anyway, so the teacher picks out one student at random.
After a long pause she says
'four...hundred years?'
a long silence fell upon the group, the science teacher, having thought she was joking, began to chuckle, after realizing she was dead serious and knowing how much of a smart-ass i am, turned to me as if to say ' say something'
after him doing so, i turned to her and said 'ITS THE YEAR TWO THOUSAND AND NINE!'
everyone laughed and the girl ran out of the room crying, it was hilarious.
(no, she was not blonde)
EDIT: i just remembered something that has happened recently, my sister, a couple of our friends were waiting to get into rock on the range (a concert, for the un informed) and she came up with the idea to yell out 'hey look its [insert band name here]!' afterwards, i said, for the sake of example 'hey look, its Rise Against!' pointing my finger in a random direction. Upon hearing this, my sister said
'WHERE?'