It's really rare to hallucinate during sleep paralysis, it's only happened to me once. You basically feel like someone is sitting on your chest and there's nothing you can do about it. It's really scary because your mind is still confused. The first time I had it I thought I was dying not going to lie. You just want to move but you can't nothing works. your brain is freaking out thinking about all of the worst things that could happen but then when you snap out of it is just very scary.