K.K.
I know which episode you are talking about. My four year old loves Thomas. I remember watching it and Andrew said it was kinda scary. We watched it again a few days later and I started saying silly stuff about the moon and music. For example: That moon sure does look silly, or I really love to dance to this music and do a stupid/silly dance. My son has never had nightmares about Thomas, but my husband accidently (yeah, right!) let him watch the shark on Jaws eat the man and Andrew had nightmares about sharks coming to eat him. We watched it again and when the shark eats the guy I asked Andrew if he thinks the man tasted like chicken to the shark and do you think he needs a toothpick? Andrew looked at me very strangly and then got a smile on his face and said, no, I guess he tasted like a french fry and you are a very silly mommy. No more nightmares!
Good luck!
K.