(written from a Production point of view)
Mark Pash appeared as an uncredited Q Judge in the Star Trek: Voyager episode "Q2". (Star Trek Encyclopedia (4th ed., vol. 2, p. 190)) He also appeared as a Starfleet officer in an episode of VOY. He received no credit for this appearance and was identified by the name tag of his trousers which were sold off on the It's A Wrap! sale and auction on eBay.