Who is Alex Krycek?
Alex Krycek in Patient X ==>

This is Alex Krycek! A real cutie eh? Well, this shrine is for people who absolutely LUURVE Alex even though he is a rat. As the leader of the RATS team, I just have to devote a shrine to one of the most famous rats to ever exist!
and here's his Bio:

Name: Alexander or Alexei Krycek

Date of Birth: Unknown.

Place of Birth: Either the US or Russia.

Alias: Arntzen

Height: 6'1''

Eye colour: Green (some people say hazel or blue, Nick Lea says green though)

Crimes he committed: Conspiracy to assassinate a federal agent. Attempted assassination of a federal agent, Dana Scully. Assassination of Melissa Scully. Suspect in the murder of Mr.Mulder. Framing a federal agent. Injecting a boy with an unknown substance against the boy's will.

 Episodes Krycek appeared in:   - ?Genderbender?(could that be Alex Krycek in disguise?)
                                               - Sleepless
                                               - Duane Barry
                                               - Ascension
                                               - Anasazi
                                               - The Blessing Way
                                               - Paper Clip
                                               - Piper Maru
                                               - Apocrypha
                                               - Tunguska
                                               - Terma
                                               - Patient X
                                               - The Red And the Black
                                               - The End

Quotes by Alex Krycek:

-Hey, I don’t appreciate being ditched
like someone’s bad date.               --Sleepless

-Mulder, if they had been here, I would have seen it.
I’m telling you Mulder, they weren’t here.           --Sleepless

-Not yet.  But he got it.  Which means he’s either found
another source, or another source has found him. Sir, if I can
recommend something. You’ll see that I have outlined several
countermeasures.                            --Sleepless

-Reassigning them to other areas seems to have only
strengthened their determination. Scully’s a problem.  A much larger
problem than you described.                --Sleepless

-You know, Chernobyl, Exxon Valdez, Three Mile Island
... they were all linked to sleep deprivation.           --Ascension

- Somewhere that you will never find me, you double-crossing son of a bitch.
                                                         --Paper Clip

-

- Hey, you go underground, you learn to live with the rats.
                                                         --Tunguska
-Tell them to kiss my American Ass
          --Patient X
- Resist or Serve
          --The Red And The Black