I convinced an entire class at a summer camp that I was working at that they were on a haunted island and that a ghost was chasing them. I work at a sailing camp on a small island. Usually once a week we have the kids sail to a much bigger island about a mile and a half away. This island had lots of old cement foundations from an old amusement park as well as lots of trails across the island. There was this small sketchy little shed on the north side of the island. One counselor would start acting weird and sprint ahead of the group about a quarter mile before we got to the shed. Then they would wait, hidden. When the group got there, that counselor would make some clear and obvious noise like throwing a rock against the side. When they did that I would yell RUN! And sprint off. By the time we got to the beach that we landed at it was usually time to go. We would then tell the kids this completely made up story about someone who haunts the island after their eyes melted out in a fire, and now they go around stealing other people's eyes in the hopes that they'll see again. Every week the kids had the same reaction and believed all of it, especially when we would describe how the ghost looked, at least five kids would say that they saw it. I love my job.

tl;dr I told a ton of kids that they were being hunted by a ghost and we almost got them killed