The original Saturday Night Live quickly became a huge hit for NBC when it premiered in October, 1975. But by the 80's SNL was in trouble. Members of the original cast were leaving for solo careers and even SNL creator Loren Michaels left the show in 1980. A revised SNL ran into disfavor by the fans and the shows ratings were falling.
When word leaked that NBC wanted to cancel SNL the shows favorite guest host, Steve Martin, had an idea to morph SNL into a new variety show he called "Twilight Theater". It was an alternative for NBC to keep it's audience instead of airing reruns of the original SNL from the 70's.
Twilight Theater first ran as a one-off special in the network's SNL timeslot on Saturday night. The idea was to bring together unrelated sketch segments hosted by a guest narrator, in this case Roddy McDowell.
Since I didn't have cable at the time, I had never seen Paul Reubens as Pee-wee Herman until he started taking his HBO show on the road to network television in 1982. Pee-wee made an appearance on Twilight Theater and it's surprising how fully developed his concept for Pee-wee's Playhouse was, containing elements from his stand-up comedy routine from "An Evening at the Improv", which I also saw starting in 1982.
Here's a link to Pee-wee's spot on the TLT Special: