Aww, this is so sweet.  Jon Stewart tears up after an autistic child (Jodi Piazza) and Katy Perry perform a duet.  If anyone can find a better copy of this clip, PLEASE POST!!!  I'm so sad he turns his face away from the camera, but then I have seen Jon cry openly in front of the camera before, so I can hardly complain. 

Oh yeah, and Tom Hanks tears up as well.

http://www.youtube.com/watch?v=MqMXy6Hvgyc