Assuming you haven’t been living under a rock somewhere, you probably have heard that The Simpsons recently became the longest running prime-time scripted TV series, beating out Gunsmoke for that honor.

Of course, real TV fans know that the honor simply refers to the number of episodes. Gunsmoke was a full hour show while The Simpsons is only half an hour. So it will be a good long time before the latter can produce the total amount of airtime that the previous has to its credit.

Over its many years since it began as a simple cartoon on The Tracy Ullman Show, a heck of a lot of celebrities have appeared on The Simpsons. Some provided the voices for characters (Kelsey Grammer as Sideshow Bob is one of the recurring appearances), others played themselves. With so many guest appearances, there have got to be some who are Overrated and others who are Underrated….

Nowadays, the show’s got enough cachet to attract (and afford) big names. In the early years, it was quite amazing when a big star was convinced to poke fun at themselves. But now? I’d say any Guest Appearance these days is going to be at least a little overrated. Like that of Lady Gaga (“Lisa Goes Gaga”, Season 23, Episode 22). It doesn’t usually help when the writers cram a lot of celebrities into one episode – it feels like they’re creating a story to fit whoever they can get to appear.

In one of those cases, though, the situation went the other way. “Insane Clown Puppy” (Season 12, Episode 3) had a couple of well-known authors appear at a book fair. Stephen King and Amy Tan voiced themselves. But the one that stood out for me was when Krusty was selling his autobiography. Lisa, I believe, pointed out that Krusty was illiterate. Krusty commented that he had it ghostwritten by….”What’s your name, kid?”

“John. Updike.”

I didn’t think much of it, until his name appeared in the credits! One of the greatest writers of the 20th century on a silly cartoon show?!?

In another instance, the “underrated” guest was essentially second billed to a bigger guest star. In “Mom and Pop Art” (Season 10, Episode 18), Isabella Rosellini plays an art dealer who believes Homer’s frustrated attempt at assembling a barbecue grill qualifies as modern art.

At a show of Homer’s “work”, Lisa squeals in excitement to see Jasper Johns there. Johns is filching things from the buffet, and snarls to Lisa, “If you tell anyone about this, I’ll ruin you.” He is later seen stealing light bulbs from the gallery, and at the end of the episode, pilfers a painting by Marge. The inside joke here is that Johns’ critics say that he stole all his significant ideas.

Yes, I’d heard of Jasper Johns and the stories about his pilfering. But I had honestly thought he was dead. So I actually did a spit take when I saw his name in the credits!!

But by far and away the most underrated appearance wasn’t that of a celebrity. Not a musician, not an actor, not an athlete or writer.

In “The Regina Monologues” (Season 15, Episode 4), the Simpsons went to England. They were greeted at Heathrow by Tony Blair. Yes, they would later meet J.K. Rowling and Ian McKellan – as one might expect.

But Blair takes the cake as Underrated – because he was Prime Minister at the time. A head of a nation’s government appearing as himself on The Simpsons!

Rowling and McKellan basically phoned in their parts. But after several months of negotiation with the PM’s office over the script and scheduling, showrunner Al Jean happened to be in London promoting the show when he got a call – “If you go over to Downing Street tomorrow and can promise to get the recording done in 15 minutes, then the Prime Minister will do it”.