It's a typical Muppet movie plot.
When Walter, the world's biggest Muppet fan, and friends Gary (Jason Segel) and Mary (Amy Adams) discover the nefarious plan of oilman Tex Richman (Chris Cooper) to raze the Muppet Theater, they help Kermit reunite the Muppets to stage The Greatest Muppet Telethon Ever and raise the $10 million needed to save the theater.
This is the seventh Muppet movie and the first since "Muppets From Space" in 1999. I expect the box office receipts to be huge all the way through the end of the year.