The season 5 episode of The X-Files co-written by Stephen King is “Chinga.”
“Chinga” is the tenth episode of the fifth season and first aired in the United States on February 8, 1998. King received a shared writing credit with series creator Chris Carter, while Kim Manners directed the episode. It is a standalone “monster-of-the-week” story rather than part of the show’s larger alien-conspiracy mythology.
The episode follows Dana Scully during a vacation in Maine, where she investigates violent incidents involving a young girl named Polly and her unsettling doll. King approached the series because he was a fan and wanted to write an episode. He worked remotely from Maine, but Carter substantially revised the script, especially the Mulder-and-Scully material.
A common mix-up is treating King as the sole writer. The official credit is shared with Carter, whose rewrites helped shape the broadcast version. “Chinga” is also sometimes remembered by its British broadcast title, “Bunghoney,” used because the original title is a vulgar Spanish term.