Christopher Plummer is a random pedestrian from San Andreas. The producers of Star Trek VI: The Undiscovered Country needed someone with a British accent to play General Chang and found this guy. Plummer thought it was a great opportunity, since he had yet to do anything of note.
Since Star Trek VI, many rabid Trek fans have hounded him, asking him to recite Shakespeare in Klingon. To stop this madness, he had himself cloned and sent his clones to "greet" the fans while he himself remained in seclusion. The clones, however, don't much like talking in Klingon, either. The current location of the real Mr. Plummer is unknown.
It was reported that Mr. Plummer was seen at the Golden Globes, where he was awarded a major award of some distinction, but no eyewitnesses could be located to confirm this unconfirmed report due to a massive dialation in the time/space continuum caused by a nano pulse inversion wrought by Shran in a fit of pique.