There is a way to make yourself hallucinate without taking any drugs or staying up for long amounts of time that I read about recently.
You need some headphones, a radio, a ping pong ball and a red light.
First you need to turn the radio on and tune it to a static noise, so it isn't on any radio stations, then listen to this through the headphones, next you need to cut the ping pong ball in half and tape both halves over your eyes, so that you can't see out of the sides of them or anything like that. Last you need to put the red light so that it is shining into your eyes, then basically close your eyes and lie there, you should start hallucinating in about half an hour or so.
Forgotten why this is, it's something to do with how the majority of your senses are immobilised so your mind starts playing tricks on you.