The writer/director of the short explained the killer's story in an interview: though he tried to be a sitcom dad it wasn't meant to be, and implied that his killing spree was his way of getting revenge. Well, the killer's face pops up one last time at the end of the introduction, indicating that he's not quite dead after all. And whose head does his face appear over at the very end? The show's main sitcom dad. Whatever that imagery implies, it seems he got what he wanted in the end.
Katie Adkins and the doctor who catches Intronitis are still aware even as they're forced to smile and pose. What must have a floating credit in front of you be like? It's the last remnant of your old self, a name only you know but no one else will call you by. And you can never make it leave, even if, like in Katie's case, the credit makes you easier to find.
Barry Tolman, the district attorney of the novel who clashes with Wolfe and Archie, is generally depicted as being a bit ineffective and pathetic. In typical Obstructive Bureaucrat-in-a-mystery-novel style, he gets things wrong, latches on to the wrong conclusion, unnecessarily antagonises the protagonists, and so forth; it's heavily implied that he wouldn't even have gotten anywhere at all with Constanza, the beautiful woman he longs after throughout the novel, had Archie not willingly took a step back in his favour. While not as virulent about it as some, he also expresses some casually racist sentiments. However, where it gets really interesting is that he's also constantly described in handsome and athletic terms; blonde-haired, blue-eyed, well-built, engaging in physical activity like horse-riding, and so forth. The novel was written in 1939, at a point where the Nazis were in power in Germany, and is a critique of American race relations. Tolman is essentially Rex Stout taking the piss out of the Aryan ideal.