At least that's a little more valid than someone thinking that Jim is basically the only Muppeteer that exists...I've seen people say something like:
"Jim sure had a wide voice range to be able to perform Kermit, Miss Piggy, Animal, and Big Bird."
Oh my...
And let's not forget, "I hate that new guy who does Kermit". Really? Do I really need to add onto how messed up that comment is.
It's interesting how people often mistake the Muppet performers for 'voice actors'. Voice is only half the performance.
Another mistake, when the Muppets made it's premiere, a well-known youtube user (I feel really bad that I can't remember her name) interviewed some Muppet whatnots (from the FAO store) about the new movie. These whatnots were clearly performed by unprofessional puppeteers, but that's okay. It was clearly just done for fun.
Anyhow, among the whatnots a lime green one with glasses. Somebody in the comments aksed if these guys were actual Muppets because he could have sworn he saw the green Muppet in "Muppets from Space" (he got an ameturely performed whatnot mixed up with Phil Van Neuter).
I remember somebody on the IMDB message boards for MFS constantly complaining about how "they changed the color of a Muppet". Evidently, he got Clifford mixed up with Floyd. More specifically the complaint was that "the orange (?) Muppet who used to call Kermit 'green stuff' is now an ugly purple".