I was surprised when I learned that the episode scripts usually transcribe Muppet inserts in their first appearances. I figured those would be their own separate scripts and they would just be listed in all scripts (including their first). Then I thought they wrote them as separate scripts which then get copied onto full episode script pages when they debut (and maybe that is the case). But then I thought of another possibility.
Maybe the person writing the episode script was writing their own Muppet/cast inserts, putting those new ones in the scripts for the episodes they are writing. I know that many of the 1970s scripts don't credit a writer, so it can be hard to know who wrote all the scripted material (and for old episodes where the street scenes don't really have a running plot, how do we know if the same writer wrote them all or if multiple writers did?).
Then again, I know that Jerry Juhl wrote Muppet inserts in the first six years, I have a feeling he did not write street scenes. Maybe those were copied into episode scripts, or maybe he wrote them as their own scripts and they were just listed in their first appearances (as I have heard that sometimes, the first appearance of a Muppet/cast/celebrity bit in a script is just listed by title). In the case of segments that get held over a year or more, do the scripts include full scripted dialogue and actions, or are those just listed by title, time, reference number, and so on?