Yes, it's another great magical Muppet's movie and I adore them all; the characters, the movies, the TV show episodes (it's the best comedy or musical TV show ever) and all the artists behind it. But here they did such a rare fatal mistake and I'm surely talking about the weird ending !!
I think it's very dangerous to involve that much, in American drama, and end a love affair by marriage !! We, as all the poor viewers, feel so free or maybe happy for the absence of its annoyance, peevishness and misery ! So we all enjoy these stories which gather 2 cute heroes as couple in love without the legitimate bond like Mickey Mouse and Minnie, Superman and Lois Lane, Dick Tracy and Tess, etc. So with all of the previous couples and their likes I bet that you feel safe, serenity and peace. Therefore when you look at what the makers of this movie had already done you'll be as mad as me !
They made the weak miserable creature (Kermit) marry his daily nightmare, the most vexatious female ever (Miss Piggy) ! This is a historical change by the measures of the American entertainment's industry ! And it was pretty normal to have a negative impact upon the audience whom just refused to bless or believe or being satisfied with that sudden marriage (even the pathetic frog didn't have the time or the proper opportunity to think or to decide anything !). Therefore no wonder at all when you know that this movie is the most failure one in their cinematic serious, grossing only 25 millions vis-à-vis 65 millions earned by the first one (The Muppet Movie 1979) five years earlier !!
Simply in this movie they took Manhattan, and my rest too !