There were quite a few celebrity cameos in the original 3 movies, and it seems to be a tradition. The only real difference was the film was marketed with more star power (at least in the US) than most of them. MupOz boldly states it features Ashanti. Actually, all the fairy tale movies heavily feature the human stars, but only Oz had the cameos. I definitely want the story to focus on the Muppets themselves this time. They already went through the getting the band back together plot that, let's face it, they needed to do. Humans should be second string even if they're important to the plot... Doc Hopper, The Holidays, Jenny and Pete.... a co-existance that isn't dominating.