I don't think it has specifically been said whether this is a Lady Gaga special with other celebrity guests including the Muppets in one or two segments (and maybe a finale with the whole cast of the special) or if the Muppets will be among the stars, like in the John Denver and the Muppets or Studio DC specials (I was surprised that the Muppets were more the stars of the Studio DC specials, I expected them to appear in a few segments).
Lady Gaga is not a "flavor of the month" pop star. I wish she was, but she's been popular for the last few years. When Weird Al Yankovic did his last album, he held it off until he could find the biggest new pop star and the right song, and unfortunately, she was it (I don't think that parody was his greatest, but I also feel that way for some of Weird Al's other lead parodies that are really popular, like Fat and Amish Paradise). I don't like Lady Gaga, I find her overrated, and I hate her nearly as much as I hate Justin Bieber. I sort of hope that the Muppets are just in a segment from the special, but if they are featured as much as Lady Gaga I'll watch the special and probably buy the DVD. And hey, it could make me dislike Lady Gaga less. Of course this special very well could feature Lips and Thog and other similarly obscure characters and make my opinion of the special biased.
Though thinking about whether my favorite obscure characters will be in this, and right now we don't know whether they will or won't, but which would be worse bias: considering a Muppet special one of the worst because one really dislikes the celebrity star, or thinking a Muppet special is the best just because ones favorite obscure character appears for even just a few seconds?