Tk-421 is a storm trooper from George Lucas's Star Wars: Episode IV, A New Hope (the movie)Tk-421 (aka THX1138 from the books)is the only storm trooper to be called by name, and is featured for at most 30 seconds. He is called on to the Millenium Falcon by Han Solo (when it is captured by the Death Star)and soon after shot. Although his part is minimal, he continues to yield an enourmous impact on the Star Wars galaxy and its many fans.

TK421 was the name/callsign of the stormtrooper in Star Wars ep. IV, who's armor was stolen by Luke and apparantly he's the only named stormtrooper in Star Wars.