Long time Muppet fans had a rude surprise on Wednesday night when Kermit the Frog and Miss Piggy performed a duet on America’s Got Talent.

As we all know, Kermit the Frog was created and performed by Muppet creator Jim Henson. Though Kermit began as an ensemble player in early Muppet projects, he soon became the puppet troupes’ lead character. When Henson died unexpectedly some 19 years ago, it was speculated that Kermit might not continue without him.

Happily, the role of Kermit was awarded to Steve Whitmire, a longtime Muppeteer who’d been performing alongside Henson for more than 10 years. His regular characters up until that point included Rizzo the Rat, Wembley Fraggle, and Bean Bunny.

Interestingly, prior to his death, Henson had been thinking about asking Whitmire to replace him as Kermit on occasions. In a 1999 interview with Muppet Central, Whitmire recalled, “I have been told that Jim had said something about it to Frank [Oz]. Not that I would perform Kermit when he died, but that he would need somebody else to do Kermit some of the time because he was so busy.”

Though it took Whitmire some time to get fully comfortable with the character, he has made Kermit his own. While the Muppet interviews and appearances are scripted, it’s not uncommon for the performers to have to make things up on the spot. That’s part of what makes the Muppets unique.

In an interview at the TV Land Awards, Whitmire commented, “If you play my voice next to Jim’s voice, they’re not the same. They’re very close, and the attitude is very close. And because I had the experience of working with Jim very closely, and knowing him, I think I gained some insight into where this character came from, from within Jim. So the number one goal in trying to continue a character like Kermit was making sure the character was the same and consistent, but didn’t become stale and just a copy. We wanted him to continue to be able to grow a bit, but also have this foundation of where Jim started… We’ve always been dubbed the ‘Muppet performers,’ and it involves acting and it involves the puppetry, and all those skills combined.”

In 2004, Disney bought the Muppet characters from the Henson company. While many fans were hopeful that the Muppets wouldn’t change, they couldn’t help but be nervous that the corporate and very cost-conscious “House of Mouse” would be making some changes — particularly when it came to the Muppet performers.

In 2005, Disney held open auditions for puppeteers to cast “alternate” performers for the main Muppet characters like Kermit, Miss Piggy, Fozzie Bear, and Gonzo the Great. It was feared that Disney would begin substituting different performers for the Muppeteers that had always performed the characters and, in some cases, had created them.

A few months later, Muppeteers Dave Goelz and Whitmire were replaced in their roles as Statler and Waldorf (the two old guys in the balcony) on Movies.com. The movie review segments ended in June 2006.

This week, Kermit and Miss Piggy made a special appearance on NBC’s America’s Got Talent. For the first time since Henson’s death, Kermit was not performed by Whitmire in a major venue. It’s not clear why Whitmire was replaced or if it’s a permanent change but it’s obvious to Muppet lovers that the substitute performer wasn’t up to the task.

Sadly, the general public may not have noticed that Whitmire had been replaced or even care that he was. If Disney feels like they can replace the veteran Muppet performers to save some money and no one notices, they surely will. If that happens, part of what has made the characters so beloved over the years will go away.

What do you think? Compare a performance by Whitmire’s Kermit on the Jerry Lewis MDA Telethon eight years ago with the recent America’s Got Talent performance. See any difference?