I recently created this riddle which requires users to look through Puzzling Stack Exchange for the correct answer. I realized that this kind of question is brittle and shaky, primarily because this kind of question is not timeless. It depends on how Stack Exchange was at one point in time. Things change. Users change. It becomes irrelevant after a certain point in time. I tired to look for elements that were more stable/established, but even those change.
There are other posts that involve Stack Exchange, so it didn't seem off topic. I think what's cool about Puzzling Stack Exchange is users try to work together for answers, to try to answer quickly, get the satisfaction of a cool problem/solution, and then move on. It's function isn't so much as a question repository, as much as it is a living community. This kind of question fits that in a way, since it's so short-lived, but doesn't fit well in a repository.
Is a puzzle involving Puzzling Stack Exchange appropriate for this site?
If not, then what would be a reasonable range of possibilities for a question involving StackExchange sites? What solutions exist to capturing the context of the question for future users that find it?