IThere is a difference between laughing with and laughing at. 2 stories:

We were playing cards in the sci fi club and in this game, we matched cards that seemed alike or that seemed funny. Green card was the word we were trying to match. Red was our card. Green card was outrageous, and my red card was Bangkok. The guide was tickled and I was winner of that round.
A guy siiting next to me was like you crazy bitch!
and we all laughed.

Another story. At a school dance, I was taking a break from badly gyrating my body to horrible rap.
I stumble across two people- a guy and a girl who I had been slightly acquantanced with over the last semester.
He greets me in a mock southern accentas and she tries to hide her snickering

Which is laughing with and which is laughing at?