Because some people appear bright until you hear them speak.
Zero, its already lit
Prism (Note: I made this joke up. Sorry if this little note refracts from the humour.)
Because opposites attract. (Told to me by 2 students today, loved it!)
They ordered 2 pepperoni pizzas, but all they got were 2 large plains.
Nothing, dogs can't speak.
Don't worry they'll tell you.
Have you ever heard anyone complaining of a elephant in their soup.
I always loved this one: (works better said out loud of course) What do you call a fish with no eyes... A FSHHH
I'm saying "Just in case." Now I'm traveling with a bigger case.
Terminal velocity.
Just before someone screams.
By appearing in television spooktaculars.