Monsters, Inc./Tear Jerker

• When Sulley says goodbye to Boo. Sulley knows he'll never see her again (he's wrong, but at the time...) but Boo doesn't know that, she's so young and innocent. And that makes it sadder. And it's when she runs up to the door and is ready to burst out to give him another 'scare' but sees the empty closet... oh man that's sad...
• A "tears of happiness" example: the ending. "Boo?" "Kitty!"
  • The only way to have possibly made the above scene even worse would have been instead of a little girl's delighted voice saying 'Kitty!', to have a young woman's astonished voice saying 'K-K-Kitty?'. Ponder it and decided for yourself.
• When Sulley accidentally scares Boo. The look on her little face is so heartbreaking... like her world just fell apart. And Sulley's reaction, as he realizes through Boo's trauma just how he's been appearing to so many children in the past, and just what a terrible thing it is to be "Top Scarer".

Sully: Did you see the way she... looked at me?

• The sequence where Sulley thinks that Boo is being horribly killed by the waste disposal. Appropriately, it's a Shout-Out to the Warner Brothers short "Feed the Kitty", where a dog finds a kitten, hides it from his mistress, and goes through the same torment as it appears his mistress is accidentally baking the poor little thing in a batch of cookies. And audiences then lost it too. Both Boo and the kitten were okay.
  • It could be more a moment of funny, since we already know she's fine and Sulley's reaction is Played for Laughs. However, considering the Adult Fear involved, one could chalk it up as Dude, Not Funny.
• If Boo crying after Sulley accidentally scared her in that scene wasn't enough, it was the somber-y music playing while she cried. The music shows up earlier after Sully gets her to go to sleep... try accomplishing two things after listening to it:

1. Try NOT to cry.

2. Try not to picture every scene of Boo, crying or otherwise, accompanied by that music.