My reaction when Charles Aznavour died, I must confess, was “Oh, hey, he’s one of those Muppet Show guests I’d never heard of.” These are most frequently musicians, I’d note. Sometimes, though, it’s various TV personalities and so forth. The plan was apparently to fill Airplane! with that sort of cameo, which they managed to resist except an appearance by Jimmie Walker that I didn’t notice until I watched the movie with a trivia track, because I’ve never seen an episode of Good Times. Which is why the makers of the film didn’t want to load the movie down with those sorts of cameos in the first place, of course.

I mean, it’s always the risk with Special Guest Stars anyway, of course. I watch a lot of British shows where you’re clearly supposed to be a lot more impressed with some of the guests than I am. The celebrity version of The Great British Bake-Off, for example. Yes, some of the guests are people I know—Michael Sheen or Warwick Davis or Teri Hatcher. And some, I know from other British shows—David Mitchell. But most episodes, it will seem clear that there’s at least one person I should know better than I do, because I’m not British.

Or take literally every time Sesame Street does one of those videos where a whole bunch of famous people are singing along to some song or another. “Put Down the Duckie” features athletes and people from Upstairs Downstairs. “Monster in the Mirror” has more athletes and the Frugal Gourmet. And that’s not even getting into all those song parodies; my five-year-old is as familiar with the Spin Doctors as I initially was with Janelle Monáe, and for the same reason. (Yes, I know her better now.) An appearance on Sesame Street is forever.

I would imagine a troll through the archives of your average late-night talk show would produce equally fascinating results. All those people who were going to be the Next Big Thing. And . . . weren’t. How many one-hit wonders have done Saturday Night Live over the decades? Sure, the first season has some pretty impressive guests—ABBA, Madeline Kahn of course, Elliott Gould—but Esther Phillips? Leon Redbone? Ron Nessen, who was Gerald Ford’s press secretary? One suspects the reason there aren’t even more guests that date episodes is that three of the guests each hosted twice.

Even when you’ve heard of them, a guest star can pin you pretty firmly in a specific time period. Friends was frankly notorious for that sort of thing. Yes, we all still know who Brad Pitt is, but can you see him on that episode without thinking about his history with Jennifer Aniston? I’d stopped watching by the time Ben Stiller was a guest, but Ben Stiller. George Clooney and Noah Wylie as doctors? Oh, yeah.

I mean, they can’t all be Paul Simon—you see Paul Simon on an old SNL clip where he’s not singing, your best bet to pin it to a specific time is by using his hair. It’s a risk you take by having guest stars. And there’s nothing inherently wrong with it, come to that; these shows are of their time and place, just like everything else. And with SNL, or The Muppet Show, at least in their first seasons, they had a hard enough time finding people to guest star in the first place. So if you get an Avery Schreiber or a Bruce Forsyth, well, that’s what happened to get the show going.

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