Michael Caine, Kermit the Frog, Gonzo and more chatted with ET on the set of ‘The Muppet Christmas Carol’ in 1992. In behind-the-scenes interviews, the Oscar winner, who plays iconic literary curmudgeon Ebenezer Scrooge, shared his comedy secret for acting with The Muppets. To celebrate the musical’s 30th anniversary, a lost song, ‘When Love Is