Why is the large spider so common in night terrors. Usually when you ask someone who's had night terrors they'll sport up a story about a large spider crawling up them or coming down towards their head.

I had two night-terrors in my 21 years of living. Both have scared me so much that I jumped out of my bed and slammed it against the wall of my room(s). They've both concerned a spider, the size of a vinyl record crawling up my chest towards my face.

What is with this spider?