1986 is a year in the 20th century.
- January 9: Luke Doggett is born to John and Barbara Doggett. (TXF: "Release")
- January 21: Colonel Marcus Aurelius Belt orders an analysis of the O ring fitting on the Space Shuttle Challenger. (TXF: "Space")
- January 28: The Challenger's O ring fitting fails and the shuttle explodes. (TXF: "Space")
- April 26: In Ukraine, one of the reactors at the Chernobyl nuclear plant explodes, creating the world's worst nuclear disaster. It was thought by some to be caused by a mythical Russian man named Yaponchick. (MM: "Maranatha")
- May 15: Dana Scully presents her senior thesis entitled Einstein's Twin Paradox: A New Interpretation to the University of Maryland. (TXF: "Musings of a Cigarette-Smoking Man")
- Dr. Doug Herman leaves the AMA over a questionable ethics inquiry and fails to renew his medical license. (TXF: "Red Museum")
- Gerald Schnauz is released from the Melvoin Psychiatric Hospital after being treated for a paranoid schizophrenia disorder. (TXF: "Unruhe")
- Fox Mulder graduates summa cum laude from Oxford University. (TXF: "Kill Switch")
- Fox Mulder then applies to the FBI Academy, and graduates with honors. (TXF: "Kill Switch")
- Dwight Cooper is arrested for Grand Theft Auto, with his brother Randall. (TXF: "Surekill")
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