Mr. Burt (played by Burt Reynolds) was an eccentric individual encountered by Dana Scully, John Doggett, and Monica Reyes in 2002. He seemed to have an uncanny way of appearing around Mad Wayne, a serial killer motivated by numerology.
As Scully and Reyes were chasing down the killer, they were trapped in a parking garage when the exit barrier locked. They discovered Mr. Burt in the garage and began interrogating him. However, it was clear that he had no help to provide regarding the case. Seeing as they were not going to be leaving any time soon, they accepted his offer to play checkers.
Both were demolished by his amazing skill. He also revealed a trunk full of compact discs, declaring that he absolutely loved all music, but preferred that which lasts. Reyes eventually concluded that the killer must have been in the garage with them, which turned out to be true. She was attacked by him and saved at the last moment by the timely arrival of Doggett.
Before the agents could speak with the mysterious individual who played checkers, he and his car were gone.
From the episode it is clear that the character of Mr. Burt was intended to represent God. (TXF: "Improbable")