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Thomas Kopache is one of a handful of actors to appear on all four of the Star Trek TV spin-off series. His largest role was as Kira Nerys's father Kira Taban, appearing in Star Trek: Deep Space Nine (1993)'s fifth and sixth seasons. He is one of only five actors to play seven or more different characters in the Star Trek franchise, the others being Jeffrey Combs, Randy Oglesby, J.G. Hertzler, and Vaughn Armstrong.
Hoshi's insult to T'Pol, "Ponfo mirann", loosely translates to "Go to hell".
Three of the prominent Starfleet officers are called Admiral Forrest (Vaughn Armstrong), Admiral Leonard (Jim Beaver) and Commander Williams (Jim Fitzpatrick). These names are an homage to the three lead actors from Star Trek (1966): DeForest Kelley, Leonard Nimoy and William Shatner. One of the Vulcans from the High Command is called "Tos", which is a reference to TOS, as The Original Series is often called.
Ensign Mayweather, when discussing the transporters, says "from what I'm told, [the Captain] wouldn't even put his dog through this thing." The dog in question is Captain Archer's beagle, Porthos. Years later, in the film reboot Star Trek (2009), a surly Montgomery Scott describes his ongoing punishment by Starfleet as a consequence of attempting to prove a transporter theory correct by transporting "Admiral Archer's prize beagle," who was transported and never rematerialized.
Up to this series, the pilot of each Star Trek series after the first included a cameo of a character from the previous one. However, because "Enterprise" takes place 100 years before Star Trek (1966), the cameo was not of a series character, but of Zefram Cochrane (James Cromwell), who appeared in Star Trek: First Contact (1996) and in Metamorphosis (1967) portrayed by Glenn Corbett.
Vaughn Armstrong, a longtime Trek actor, appears here as a human for the first time, bringing his total Trek appearances to eleven - as 9 different characters, and 7 different species (human, Cardassian, Klingon, Romulan, Borg, Vidiian, Hirogen).