Due to a laundry mix up, I currently have one black sheet and one white sheet on my bed. This morning it served as a trigger. I dreamed I was in a hotel room and noticed that the bed had a black sheet and white sheet on it.

"Wait," I said. "Why would a hotel have this weird combination of sheets? Isn't that how my bed at home is? Oh ... I'm dreaming!"

So it was kind of funny. I guess having something unusual near your bed may serve as a trigger