When the Muppets first began, they started as fully-formed characters with no set age, though were clearly in their adult stages. Though characters, such as the Muppet residents of Sesame Street, are given set ages, they've remained the same age and look since their debut. As such, the subject of the characters' ages versus their physical appearance has been referenced many times for the sake of a joke.
- The Muppets: A Celebration of 30 Years honors Kermit the Frog's 30 birthday, as well as the entire Muppet family. However, Miss Piggy denies being grouped with them, explaining "there's no way moi could be 30" and adds that she is a "child star" because her debut on The Muppet Show was 10 years prior. Harry the Hipster also questions how Kermit looks better currently than he did on Sam and Friends. "That's one of the advantages of being a Muppet," Kermit responds.
- In Sesame Street: 20 and Still Counting, Bill Cosby asks Big Bird how he's remained six years old for (then) 20 years. Big Bird replies, "Just lucky, I guess!"
- On an appearance on The Tonight Show in 1996, Jay Leno asks Kermit how he retains his youthful look. Kermit claims frogs age at a different rate from humans and he makes two annual visits to an anti-aging clinic where "they rub [him] up against Dick Clark." He adds his exercise regimen helps, performing leap frog.
- In a 2005 appearance on Rove Live, Rove McManus compliments Grover's appearance after 35 years of Sesame Street. Grover notes it's because of his workout routine and remarks, "You do not get a body like this naturally, you know." He is however able to do more than one push up afterward.
- In a 2010 "Ask Elmo" video, YouTube user CuddlesTaffy asks Elmo, "How come you never have birthdays and you stay 3 for the rest of your life?" Elmo corrects the user, saying he does have a birthday (February 3), but claims his agelessness is due to being "a monster thing." He adds, "You should be so lucky."
- In the opening sequence of The Muppets, Walter and Gary's childhood is shown. While Gary ages throughout the sequence, Walter physically remains exactly the same, hinting at his Muppet roots. Later in the "We Built This City" montage, Fozzie Bear comes across an old photo of himself in The Muppet Theatre. He laughs at his "80s haircut," unaware that he looks almost exactly the same.
- In a Q&A on a New York Times Snapchat story, Grover responds to a question about his age by saying he's "older than a breadbox, but young enough to live at home with my mommy."
- Bert and Ernie are asked about their age on a 2014 appearance on Oprah: Where Are They Now?. They simultaneously give different answers (Bert, 52 and Ernie, 25).
- While promoting the forty-fifth anniversary of Sesame Street on Today (Australia), the anchors asked Elmo and Abby Cadabby how they had avoided any visible aging, snarking that "everyone knows Miss Piggy's had some work done". Elmo replied: "A very good lint brush and a couple tumbles through the dryer". Abby equated her youthful good looks to a fairy's naturally slower rate of aging, and her general love of sparkles and smiles.
- In a 2016 appearance on Last Week Tonight with John Oliver, John Oliver acknowledges to Elmo and Rosita that their resource video, Lead Away!, was released 20 years ago and compliments their youthful looks. Rosita claims she uses moisturizer and Elmo chalks it up to his gym trips.
“A perk of being a frog is that your look doesn't really change. This is why I've never had to change my driver's license photo.”
- At a 2016 appearance at Vulture Festival, Fozzie claims he goes to a fur colorist to keep his youthful looks. Kermit attributes his to running from Miss Piggy for many years.
- In an interview with 60 Minutes (Australia) in 2019, Abby Cadabby, Big Bird, and Elmo note the strangeness of having been around for fifty years and not having grown any older in that time. Elmo explains that "monster years" and "people years" are different, and he isn't sure what the conversion rate is, but has noticed some eye bags underneath his fur lately. No one has any idea how to calculate "bird years".
- Elmo would reuse the "monster years/people years" line (and the eye bags joke) while promoting the show's fiftieth anniversary on Access Daily.
- In a video for Vanity Fair, the interviewer asks Big Bird if he has truly been six years old since 1969. Big Bird admits that he is still learning his numbers, but that sounds right. According to the lie detector, this, like everything else Big Bird had to say in the interview, is a true statement to the best of Big Bird's knowledge.