The character of Yoda in The Empire Strikes Back was voiced by the legendary muppeteer Frank Oz, who also does the voice for Miss Piggy. Mark Hamill was a huge fan of Oz and of the muppets. When he first met Oz at a rehearsal on the Dagobah set, Hamill asked if he would be part of a practical joke—Hamill wanted Miss Piggy to do an impromptu cameo in the scene. Oz readily agreed. But the rehearsal was taking forever and by the time the scene came up, Oz surprised even Hamill.
In the scene, Yoda tells Luke to follow his feelings. Just as Luke says that he has followed his feelings, out pops Miss Piggy, howling, “Feelings!? You want feelings? Get behind the couch and I’ll show you feelings, punk. What is this hole? I’ve been booked into dumps before, but never like this. Get me my agent on the phone!” Luckily the cameramen got this little gem on tape, and it now resides on the film’s blooper reel.