I take the logic approach, like one of the other mothers said. My daughter who's 5 has done this a few times. I just went into her room and asked her "Are monsters real?" Then when she said "no", I asked her "well then why are you pretending to be afraid of them?" I think that kids will come up with just about any excuses for them to get out of bed, and if they find one that works, they'll stick with it. I think that the spray idea is cute, but I think that you're setting yourself up for having to "monster spray" every night for the next few years. Plus, it's great to feed your child's imagination, but in a productive way, not in a way that creates and allows fear. If I ever am called into Aryana's room, I'll ask her what's wrong, and if it's a shadow or something, I shine a flashlight at it and explain to her that things look different at night, but that doesn't mean that they're scary. It's the same things that are in her room during the day, but the lights from her nightlights cast their own shadows. If you explain things logically, the problem will stop. Kids are extremely smart!