Dave Grohl is the "Gandhi of rock'n'roll", according to The Muppets.

The Foo Fighters frontman appeared alongside the puppet group in their eponymous 2011 movie. Kermit the Frog, Dr. Teeth and the rest of the characters thoroughly enjoyed working with the rock god.

"You may find this hard to believe but it is most certifiably true. My man Dave, aka the Grohl-man, is one very peaceful dude. Absotively non-violent. The Gandhi of rock'n'roll. And to my knowledge he never actually fought a Foo," said Dr. Teeth.

The Muppets have worked with many famous faces over the years. Sir Michael Caine featured in their 1992 film release The Muppet Christmas Carol and has a special place in Kermit's heart.

"Sir Michael is an incredible actor and one of the kindest and most generous people we have ever worked with," he told Q magazine. "I'm still not sure what got into him to agree to do our movie, but we are forever in his debt and Sir Michael, I promise that the cheque is in the mail, end of the week at the latest. Sincerely, he got along with everyone, even Miss Piggy and after she made repeated attempts to permanently borrow his Oscar."