TelevisionThese television series featured conlangs as far back as the 1970s. All are available on DVD for your viewing pleasure.
Frank Herbert's Dune (2000)
This Sci-Fi Channel television mini-series adaptation has dialogue in the language of the Desert Fremen.
This series addressed the problem of alien communication on several episodes. The most famous conlang word in the series was the expletive frell as in What the frell! and I am not Kirk, Spock, Luke, Buck, Flash or Arthur frelling Dent.
Game of Thrones (In production for HBO)
This series, based on the series "A Song of Ice and Fire" by George R.R. Martin, is to feature the Dothraki language created by David J. Peterson. For press coverage of Dothraki, click here.
Land Of The Lost (1974-1977)
A Saturday morning live action series. Prof. Victoria Fromkin created the Pakuni language. Pakuni predated Klingon by a decade as a conlang associated with a television series.
Star Trek: The Next Generation (ST: TNG, 1987-1994)
Star Trek: Deep Space Nine (ST: DS9, 1993-1999)
Star Trek: Voyager (1995-2001)
Star Trek: Enterprise (2001-2005)
Of course, not every episode of Star Trek featured Klingon, Romulan, Vulcan, or another conlang. Klingon was not invented until the Star Trek movies. Some television episodes using Klingon dialogue include: ST: TNG: A Matter of Honor, The Icarus Factor, The Bonding, Sins of the Father, Birthright Part II, Redemption I & II; ST: DS9: The Way of the Warrior. ST: Enterprise did not always use canonical Klingon (tlhIngan Hol) but Klingon-sounding words (called Paramount Hol by its critics, in reference to the production company).