The pilot
The pilot is a long form style invented by Ethan Rosenberg and his improv group Code Blue for his senior thesis.
The ref introduces the scene as the rarely-seen pilot for an (imaginary) famous classic TV show. The audience suggests a TV genre and some other details about a TV show, such as location or characters. Improvisors then come on-stage as TV writers brainstorming ideas for a new show. They mention all the audience's suggestions and then think of some more. They clear the stage.
Improvisors then act out the show's pilot, incorporating all suggestions. Every seven minutes or so, they pause the action and act out a few very short scenes as commercials.
After about twenty minutes, the episode ends. The ref comes back on stage and introduces a reunion of actors from the show. Improvisors come back on stage, this time acting as the actors of the characters they just played.