Yep. I encountered it well before the Dope in grammar school or possibly high school (80s/early 90s). The admonition was something like, if you’re going to break out into a numbered or bulleted list, it has to be at least three items. Otherwise, just in-line it.
The joke is a bit of meta-humor about comedy writing, and the trope of writing two normal things and then a punchline. Don’t read anything more into it, because that’s all it is.
However, last night I was reading to my kids a story with included a list of 4-5 character names, and one was Opal. After reading the name I said, as an aside, “Hi Opal!” and kept reading. My kids stopped me and wanted me to show them where it said “Hi Opal” and I had to admit that I made that part up.
I throw in little jokes pretty often when I’m reading to my kids, in the same tone of voice as for the rest of the text, to see if they’re paying attention. They usually are. One common interjection: “He stroked his beard thoughtfully,” after it tickled my funnybone in a book I read long ago. Bonus points if I get away with it in referring to a female character.