In a scene not too long after Tom Cruise attempts to revive a hooker who has OD'd, he is speaking with an older gentleman. The three are in a bathroom and the hooker is passed out on a chair. One of the shower or light fixtures toward the left of the screen is shiny, and in a shot during which the camera briefly tracks in reverse, you can see the camera, cameraman and the focus puller reflected. It's pretty clear and not all that fast.
The strange incantation heard at the beginning of the orgy scene is a fragment of a Romanian Orthodox Church sermon played backwards. If you play it backwards you'll notice that there are two main voices (in the movie is supposed to be only one - the voice of the "great priest") and a choir.