George

Me:  "If you can tell me who the first president was by tomorrow, I'll give you extra credit."
Student #1:  "It was George Washington...who doesn't know that?"
Me:  "Technically, there was one before him."
(silence)
Student #2:  "No there wasn't.  It was just the great J.W..  That's it."
Me:  "J.W.?"
Student #2:  "Yep!  George Washington! J.W.!"
(silence)
Student #2:  "Wait..."
Me:  "Yea, what does J.W. stand for again?"
(silence)
Student #2:  "Ohhhhh.  It's G.W.. G is for George."
Me:  "Well done."