C.C.
My five year old boy was also afraid of EVERYTHING for about 6 months during his 4th year. I could see him in the bathroom from my office 10 feet away but I had to go in with him each and everytime he went for 6 months to "protect" him from sharks in the empty tub LOL! He was also afraid of the mummy toy he begged for for 6 months. Money well spent!! I also worried about how he was so afraid all the time of everything and finally he just got over it. One day instead of being afraid of everything he wanted to start hanging out in graveyards. Weird obsession don't ask!! LOL So scardy cat is really normal for a little guy with a big imiagination.
don't sweat it and remember that the next obsession could be ANYTHING so don't worry about that one either. (Our new obsession around here is dressing like the dukes of hazzard.)