I was very cautious about introducing anything scary to my oldest. Unfortunately, while he was sick a few weeks ago my ds let him watch "Thomas the Tank Engine -- Spills, Chills, and other Thomas Thrills." The feeling in the video is pretty scary. All the stories are at night and the music is pretty ominous. There is one story where a boulder is rolling toward the engines and they talk about how the boulder is watching them. There is another story where some cars plunge off a bridge into the water below. And something that happens to Toby was of concern to Christian, although I can't remember what he is talking about.
After watching it he began talking about it, especially the boulder, and the Toby thing. He found boulders everywhere in our house, including the lightbulbs in his ceiling fan. He began being afraid of the dark and wouldn't walk down the hall alone, even with the light on. All the doors in the hallway had to be closed. To top it all off, he started wetting the bed at night because he was afraid to go to the bathroom. Leaving the bathroom light on and a light in the hallway didn't help.
I made him some "Go Away Monster Spray" and that seemed to help a little. I put plain water with a few sprays of a lavender room spray in a small spray bottle for him, and labeled it. Every night before bed he would spray it on his bed and in his closet. I think it makes him feel better knowing that it's there.
I didn't tell him that there were no such things as monsters, and I was actually the one who gave his fears the monster name basically so we could talk about it. We did tell him that the monster spray worked on boulders too.
He seemed to do well with the idea that we gave him some things to do to cope with the monsters, ie the spray. I told him that the monsters don't like the way it smells so they leave. He also had to know that we locked all the door and windows before bed so that no monsters could get in.
The fears lasted about two or three weeks, then they faded. He will now walk down the hall without the light on, the doors don't have to be closed, and he typically doesn't think to use the monster spray anymore, although it's still there. I know there will be more "monster" issues in the future, but I hope they don't involve wetting the bed again. That was a bummer.