Only once, in December of '05.
I don't have any knowledge of how I got in there, but I was laying on a narrow table looking DOWN at the table. I knew I was in a UFO when I saw large stainless steel tubes, about 2 feet LONG, running in different directions connected to a machine that resembled a vacuum cleaner. Then a voice said "this is going to be uncomfortable".
I had never seen anything quite so freaky or futuristic.
I heard echoing voices and saw movement, but couldn't make out what kind of creatures they were. I do recall that they were all wearing turquoise uniforms with face masks.
Without warning, a hand came from behind me and covered my face with something smelly.
Several hours later I woke up in the recovery room.