Vader: Luke, I am your father.
Luke: That's not true! That's impossible!
Vader: And Princess Leia is your sister.
Luke: That's not true. That's improbable.
Vader: And the empire will be defeated by furry midgets.
Luke: Now you're just making stuff up!
(span of time)
Vader: (smoking) And when I was a kid, I made C-3P0. And the Force? That's really just bacteria in your blood called midichlorians.
Luke: (leaving) Look, call me when you get serious.
That's not exact, but it was along those lines