Grandpa's Dream

I remember seeing a cartoon where a dog is sound asleep and yet his legs are running as fast as they can.  In the bubble above his head he is chasing a rabbit.  Grandpa always goes to bed a while before I do, and the other night when I got into bed he reached over and took my hand.  It was so wet that I reached over and touched his face and he was really sweaty.  I asked him if he was all right and he said "yes, why."  I replied that he was sweating.  He then said--well I should be; I have been running like crazy!  He then turned over and went back to sleep.  I wish I knew what he was running after!