If you've heard Grover, Bert, Miss Piggy, Fozzie, Animal or Yoda, then you know Frank Oz's voice. He was the creative force behind many of The Muppets and he's in a new documentary about working with Jim Henson, the mastermind behind them and many more beloved characters. | Want to support 1A? Give to your local public radio station at donate.npr.org/1A and subscribe to our podcast. Have questions? Email the show at 1a@wamu.org and find us on Twitter @1a.