(written from a Production point of view)
Mark Pash appeared as an uncredited Q Judge in VOY: "Q2". ((Star Trek Encyclopedia (4th ed., vol. 2, p. 190))) He also appeared as a Starfleet officer in an episode of Star Trek: Voyager. 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.