Three run-throughs of pilots were made. The first two run-throughs were taped at NBC Studios in 1976. The third run-through was taped at KTTV Studios in 1977.
After the first run-through of pilots, NBC wanted the show to have celebrity panelists instead of unknown comedians. Producer Ron Greenberg wanted to have at least one the panelists be an unknown comedian. He pushed for David Letterman to remain for the second run-through. But the network replaced Letterman with Jay Leno.