Grover said:
I think were probably going to see the first five season premiers (1,131,276,406,536). For intrests mainly I was listing the characters who didn't make an apperance in the first five premiers.
Charcters included in Episodes :
Big Bird
Oscar the Grouch
Cookie Monster
Kermit the Frog
Grover Monster
Ernie and Bert
Herry Monster
Guy Smiley
Herbert Birdsfoot
Sherlock Hemlock
Mr.Johnson
Simon Soundman
Snuffy
Characters not Included:
Lefty the Salesman
Prarie Dawn
Farley
The Twiddlebugs
Professor Hastings
Roosevelt Franklin
Placido Flamingo
Don Music
Mumford the Great
Biff and Sully
Harvey Kneeslapper
Forgetful Jones
Beautiful Day Monster/Baby Monster/Scudge
I have been thinking about this a lot lately as well. I've been looking at the pages for the season premiers at Muppet Wiki. Of course, Noggin did edit a few minutes from each episode. The contributors only know of what was edited from the first episode, and I think a contributor knew what was edited from one other of the first five season premiers, so those characters you listed as not being in the season premiers might have still been in them.
And you are wrong about some of them. The following did appear in season premier episodes:
Farley (season 2 premier)
Prairie Dawn (season 4 premier)
Roosevelt Franklin (season 4 premier, and I think he's also in another of the first five premiers, though not seasons 1 or 2)
Also, Placedo Flamingo and Forgetful Jones were not around during the first five seasons. I am not sure when the Tweedlebugs made their first appearance. And don't forget about Sam the Robot, who was introduced in the fourth season premier. And I guess you can add Roosevelt Franklin's Mother, Little Jerry and the Monotones, and Chris and the Alphabeats to the list of characters from the first five seasons who were not in the season premiers (unless Noggin edited their material from those episodes).