I've also experienced odd shroom-like hallucinations while my body has been exhausted from not eating all day, then going out all day smoking pot, in the sun. I had heatstroke, and i got in the door and in the kitchen i felt like i was on shrooms.
I even had hallucination like on shrooms, and would close my eyes and see patterns and pictures intertwine. It seems as though whenever i am barely concious, or have nausea, i start trippin'. I think this makes alot of sense, because while your on a mushroom trip, you feel barely concious, and when you get very intense visuals, you will feel nausea for a minute or two. Mabye its because my mind got used to the feeling of nausea, then a hallucination.