What was the matter with the writer who didn't have an invitation to the show?

Question

Nearing the end of King of Comedy, when the show that Rupert "bought" himself into starts, there's a writer with his family at the (back?) entrance, supposedly one of this evening's show guests. But to his surprise he isn't actually on the invitation list and starts to argue with the porter, until he just runs into the studio, alarming the guards thereby. This confusion is used by Rupert to sneak into the studio.

But I didn't quite get what the background of this incident actually was, especially since the writer is then further questioned by the guards about his background, all of which seemed rather unrelated to the rest of the story. Sure, it provided Rupert with a way to sneak into the stuido, but had he just introduced himself as "The King" they would have had to let him through anyway. And it seemed quite a coincidence and unusual event to be entirely unrelated to the story at all.

So what is the actual background of this incident with the writer and his supposedly lost invitation that further ties it into the rest of the movie's story? Was this really just some totally unrelated coincidence (or maybe he was just supposed to be dropped by the changed program due to Rupert's shenanigans)? Or was that maybe even facilitated by Rupert himself somehow in order to silently sneak into the studio (but why would that have been necessary)?

Answer 1

One of your assumptions was indeed right. The writer (McCabe) was just bumped from the show. Here's the conversation between the network executives from the original script:

CROCKETT: Let me see your list. Any one of these a writer?

THOMAS: McCabe. The Vanishing Siberian Tiger.

CROCKETT: He's out.

CATHY: What if we don't run this King guy? Who'll fill the time?

CROCKETT: We'll stretch the other guests.

McCabe is the third guest, a writer and lesser known than the other guests that night (Shelley Winters, Gore Vidal and Tony Bennett). It's not uncommon to bump these sort of guests in such emergencies. This is why his name is not on the list, and when he barges into the studio, the cops and feds mistake him for the King and apprehend him.

As for Pupkin planning all of this in advance, there's no indication of it in the film or in the original script. I can't imagine how he'd somehow orchestrate this to sneak in anyway and as you said, he didn't even have to sneak in. At most, he took advantage of this fortunate incident to get him closer to the stage.