Are you referring to "during Jim's time" or in general? Before his reemergence Christmas 09, he last appeared in Muppet Christmas Carol.
Hmm... I forget about that... but even during those last years with Jim, Lips really didn't make much of an impact, but he was there when the Mayhem was on occasion. Just... a lot of Muppet projects since didn't feature the Mayhem all that much. I forget to what extent they were used (if any) in JHH, but Solid Foam was much more of a presence.
Given that the only things in the late 80's were TV specials and Muppet Babies and kid's videos, the Mayhem was a part of some of that. The specials and maybe the videos at least. Can't remember if Lips was in MFC at all, though.
I wonder if Dr. Teeth and Floyd are really too different from each other. Both are cool characters, both enjoy things that are hip and groovy, both act like leaders (Dr. Teeth has his name in the band title and does most of the lead singing, while Floyd interacts more with characters outside the band, having the advantage of not being a Jim Henson character and being the only EM musician whow as the main character of his performer).
That's trues, actually... Though I think Teeth definitely has something a little different than Floyd. albeit subtlety... and I do think is is due to Jim performing Kermit backstage and Floyd having more of the lines. Floyd's backstage presence also has a lot to do with being one of Jerry's big main characters, so it would make sense to have one of his characters in a scene with Kermit, anyone of Frank's and or anyone of Dave's or Richard's.
But it seems that Teeth's jazz background and Floyd's classic rock background give a slight subtlety in tone. Floyd is a bit more laid back, where as Teeth isn't so much laid back as he is smooooth. Plus, Teeth can be a little more bombastic if he wants to. He just never really had the same extended use Floyd did (again, due to Jim as Kermit)... plus, he does have that leadership quality, and he is the brains of the outfit. I'd say, if anything, being the leader gives him a certain distinction, that while not obvious, makes him just a bit different from Floyd.
That said, trumpets aren't usually present in Rock.
Then of course, there's the whole Steve aspect. Steve really didn't have many major characters until the end of the show, and Rizzo was his signature character... while he was in GMC briefly, and TMM sorta kinda... he really took off in MTM.