X-files and Terry O'Quinn's (Locke from lost) multiple characters?

Question

why does he play different characters in the show/movie? can any one explain this to me... as far as I tell these are all the people he plays

1. FBI agent michaud from the x-files: fight the future movie who blows up in the building in the first 10 min of the movie

2. creepy cop tillman from the show who gets BJ preggo, who turns out to be the granddaughter of a serial killer who cuts sister into the chest of his victims.

3. mysterious guy from the show who spys on scully and who calls scully to "help" mulder, but turns out the be a super soldier trying to kill mulder and who gets sucked into iron rich dirt..and dies (?) i guess....

this is what I have seen, not sure if his in anymore episodes, but im sooo confused! help please :)

Answer 1

What Asami said is correct - I believe the girl she was referring to is Jewel Staite, best known as Kaylee on Firefly, who also played multiple characters on Stargate Atlantis (she was a Wraith girl in one episode, and then a main, recurring character starting a couple seasons later).

Answer 2

If the creators of a show really like an actor, they'll wait several seasons and then use the actor again as a different character. They give enough time for most people to forget about the who played the part. The X Files did the same with a woman who played a waitress who had a connection to a young girl, (the girl was from the old Disney show "Flash Forward") who had been kidnapped. They used the woman again several seasons later because they liked her as well.

They just like to give opportunities to actors they like.  

Answer 3

If the director of a show really like an actor/actress and they have a good range to play different characters and make them believable this is more in their advance to be hire in up coming show or movies. that is why you might see one actor/actress play different characters or dual on a show.  hope this help you..