This New Yorker article entitled The Outlaw The extraordinary life of William S. Burroughs wrote:
But Burroughs liked his own growing fame. He gave readings to full houses. Appearances on “Saturday Night Live,” in 1981, and in Gus Van Sant’s “Drugstore Cowboy,” in 1989, spread the popularity of his gentleman-junkie cool.
This YouTube video entitled Guest Performer: William S. Burroughs - Saturday Night Live has the entire recording of his performance.
I've never seen a writer on SNL as the "guest performer". Ranker mentions:
Since its premiere in 1975, SNL has had more than 600 unique musical guests.
Most "guest performer"s are usually musical in nature.
Besides William S. Burroughs has any writer been on SNL as the "guest performer"?