Link - one of the main supporting characters that has yet to really fully resurface after the losses of Henson/Hunt. Too classic a character to remain out of it for so long.
Would love to see Thog rebuilt and used.
Mahna Mahna - yes he did make some nifty comebacks between MuppetFest and the Bandana psa thingie, but i miss just seeing him as a background character, popping up on screen in unexpected moments. Heck if the Snowths can pop up on Muppets Tonight, Jerry Lewis Telethon, and Studio DC, Mahna can be part of a crowd scene (if i was Claire, i wouldn't need all the Muppets to keep me company of Christmas, just Mahna popping out of a fruitcake yelling Mahna Mahna would do nicely)
Gloat - we've had the Blue Frackle still continue to make random appearances, but not Green...and somehow that just doesn't seem right.
Lips - nuff said.
Flash - i don't need the whole Solid Foam band back but this character has a lot of potential as a stand-alone puppet (and may i say one of the few Muppets i had a "Muppet crush" on)
Wayne - on the Muppet Show, he survived past season one, but not much past the end of the series itself...and yes, he wouldn't be totally the same without Richard Hunt but man i still would love to see him back in some way (again if even as a background character)...man oh man, if i had pursued my dream of being a Muppeteer, *I* could have done him as i can match him extremely well vocally!
Gladys - again another Hunt character that was as great as she was especially due to Hunt's performance, but i've waited since 1978 for her to appear again and i suppose i've never given up still waiting.
Nigel (the conducter)...since he rarely spoke (aside from his debut), he could totally be easily brought back...i love his look and how i would love to see him waving his baton in front of the Muppet Orchestra again.
Marvin Suggs - always has been among my top five faves...he's one of those Muppets that make my eyes go wide and jaw drop whenever he's onscreen and would love to experience that again!
Phil Van Neuter - one of my fave MT characters and i'm happy that he did get some good exposure after the series wrapped, but that has died down.
Carter the Butler - again, another Muppet who had a little bit of post-MT glory, managing to steal the few parts of Muppets From Space he was in.
Taminella Grinderfall - have always wanted her to make a cameo, and now with Jerry Juhl no longer with us, this is even more non-likely as it's been for the last few decades, but even he Jerry was still with us, she'd probably be voiced by someone else anyway. But i would love to see her make the most random appearance be it among a crowd scene or with a line or whatever...so many of these, i'd be happy to see as background extras...i mean if some other long-thought-would-never-be-seen-again puppets like George and JP Gross could be seen in the 1990's, is it too much to ask to see Hilda, for example among a group of random Muppets in a crowd scene? But back to Tammy, the ultimate surprise cameo would be in some restaurant scene where Kermit is in a booth sitting by himself probably because he just had an arguement with Piggy who left in a huff or a group of Muppets all took off as the bill is brought to the table...and Kermit's there at the table gulping over whatever just happened, and just as it seems like the scene's about to cut to something else, all of a sudden Tammy pops up out of nowhere working as a waitress offering "Have a popover Froggy?"
Beautiful Day Monster - just a classic puppet with a lot of great history that would make a good addition to the group of extras.
Fleet Scribbler - too edgy in 1977, but would work well in today's tabloid obesessed society.