I don't exactly know what you're looking at. Most of the artwork I've seen for the Muppets really seems to fit. But then again, most of it is done by people like Frith, Marie Severin... people who really know the feel of the characters.
Though it is often we see artists slip into their own style. Like Gilchrist's later muppet strips. They seem to be a lot looser than the earlier ones when he was trying to make them look as much like the puppets as possible.
Personally, I still think they need to get a variety of artists on this project. Not that I don't like the guy's style of art work, but it seems to fit shorts rather than full multipage storylines.
And Was Once Ernie... I wonder if it's possible for you and that other guy to contact them about asking if you can work somewhere in a future issue. I bet you guys would REALLy do a great job there.
It reminds me of a story about the one shot Mighty heroes comic Marvel published... Ralph Bakshi wasn't contacted (he created them for Terrytoons, after all) and didn't know about the project, and would have loved to have been behind it.