Buffy - 1x10 - Nightmares
Firstly, due to the dream-like nature of this episode, it’s important to sort everything in to two categories: direct and indirect. The Ugly Man’s existence is a direct result of the nightmares. When Billy wakes up, The Ugly Man no longer exists. Laura being attacked is an indirect result of the nightmares, and when Billy wakes up, I’m assuming that it doesn’t undo Laura’s attack. Because of this, some damage (direct) is reversed at the end of the episode, but other damage (indirect) remains. I don’t know for sure if this is how it works, but otherwise I could just go “lolz everything gets fixed at the end this episode has no damage” when, clearly, a lot of things get broken.
The Ugly Man knocks Laura into something when he attacks her in the basement. It’s unclear what it is or if it breaks, but it does fall. This damage is indirect, so whatever it is stays broken. The school is later seen in of disrepair, but nothing seems to be damaged. There’s mostly just a lot of trash and plastic tarps everywhere. Regardless of the exact damage, it’s all a direct result of the nightmares and therefore returns to normal when Billy wakes up.
The hospital is also seen in a state of disrepair. It’s much worse than the school. Equipment is thrown everywhere, papers are all over the floor, decorations are falling from the wall, and a crew of people can be seen rushing into a patient’s room with a defibrillator. It’s possible much of the equipment is failing. Fortunately, it’s all directly caused by the nightmares, and the hospital returns to normal working order as soon as Billy wakes up.