With some contributors to Muppet Wiki having Sesame Street scripts from a "trusted source", I wonder if we'll figure out the episode that introduced us to Telly Monster in his current, better-known personality as opposed to his original TV-obsessed personality, due to the fact that Caroll Spinney was suddenly unavailable and they changed the episode they taped from a Big Bird-centered episode to a Telly-centered one.
If they were just replacing Big Bird with a character who was suddenly given a new identity, would they have bothered to change the script? Maybe they'd cross out Big Bird's name and write in Telly, I think typewriters had something that could cross out names though I think they would have done it in pencil. But they easily could have just told the cast to refer to him as Telly instead of Big Bird (and in the old days, it was common for them to correct their own mistakes on-screen - in fact, it seems it was also common for scripts to allow a lot of improv because of this, though I don't know if that changed by season 10/11). I think one of the contributors with these trusted sources said that some scripts seemed to be transcribed by somebody actually watching the episodes as opposed to the actual pre-taping scripts (but what would be the odds that this Telly episode would be among them?).
I've read that many of the scripts say "final aired version", I wonder if that note was made to the scripts after the street scenes were taped or after the whole episode was edited together (and maybe after test screenings) or if it was put in after the episodes actually aired.
Though I guess one possible way to figure it out would be if a script mentions Big Bird but the program guide at the CTW Archives mentions Telly instead (but the program guides often aren't that detailed - the season 11 program guides in particular look like full episode rundowns but a lot of scene descriptions are very generic, with things like "Letter Recognition: C (three segments)" or "Word Recognition: Stop".