My toddler son is obsessed with trains. When I say obsessed I really mean it. All he ever wants to watch are Thomas the Train videos, he plays with his toy trains constantly, turns everything into a train (if I give him markers to color he turns them into a train, magnets on the fridge, etc) runs around going "woo-woo" all the time, he can spot the tiniest little picture of a train in any book(he has to get our attention to show us). If I turn his Thomas video off he goes "where Thomas?" and gets really upset. Is this "normal"? He doesnt even want to leave the house anymore because he wants to play with his trains. I mentioned this to a friend and she says it could be a sign of autism?? I looked up signs and he doesnt seem to exhibit any..Does my friend just have no idea what she's talking about?