Why was I laughing in my sleep ?

I remember just before I went to sleep, like as I was in that 'half asleep half awake' mode, I was laughing. Then I remember having this weird dream about being on a plane with a SWAT team. But I'd watched a tv show about that prior, so that doesn't bother me. But then when I woke up from that dream, I was hysterically laughing, my dream wasn't even funny? Why was I laughing those two times?