I was thinking today about comic strips which have in some way transcended their origins.
Maybe the best example is the Bechdel Test. I doubt most people who know the concept could tell you the name of the strip it came from, but lots of people know the concept.
Another Far Side reference: in the strip below, Gary Larson jokingly coined the term “thagomizer,” for a stegosaurus’s tail spikes. The term is now commonly (if informally) used by paleontologists for that anatomical structure.
The OP mentioned xkcd, and I think one of the most referenced and forwarded panels is the Tech Support Cheat Sheet, at least among us IT guys who do computer support on the side for our relatives and friends. It’s also printed out and pinned to the wall in every IT department office I’ve ever been to:
Maybe, though it appears that that’s a case of others bastardizing the original strip/artwork – as far as I know, Bill Watterson never actually depicted Calvin peeing in a strip, and as this article notes, the commonly-used picture seems to have been adapted from an image of Calvin filling a water balloon from a water faucet.
There’s the term "sealioning’, meaning to subtly troll members of an online forum with persistent and repetitive, but on the surface, or at least initially, polite and innocent questioning. from Merriam-Webster:
Sealioning refers to the disingenuous action by a commenter of making an ostensible effort to engage in sincere and serious civil debate, usually by asking persistent questions of the other commenter. These questions are phrased in a way that may come off as an effort to learn and engage with the subject at hand, but are really intended to erode the goodwill of the person to whom they are replying, to get them to appear impatient or to lash out, and therefore come off as unreasonable.
Well, I don’t know whether OP is asking for a single example of a strip or a theme or trope that can be found throughout the run of a strip, but if you describe something as being like Calvinball, there’s a pretty good chance that person will know what you’re talking about.
Same with Lucy and Charlie Brown and the football.
I’m pretty sure the OP is looking for single examples, not recurring elements or tropes.
The trouble is, AFAIK we don’t have a word that means a single “episode” of a comic strip (although “panel” would work for a one-panel strip like “The Far Side”).
“Lucy and the football,” which was a recurring theme in Charles Shultz’s Peanuts, has become a metaphor for bait-and-switch tactics, and gullible people who continue to fall for them.
