Consider the following pun:
"What do you say when you see an empty parrot cage?" "Poly-gone"
It's funny in the way that bad puns are, but it had a sense of novelty when my grade school teacher told it shortly after we started learning geometry. The pun was relevant then, the concept it referenced was on the cutting edge of the classrooms knowledge. Now that I'm older and take the definition of a polygon for granted, the novelty of the reference is gone. Even if I'd never heard it before and it was presented in the proper context for a geometry pun (whatever that would be) it wouldn't be the same. I could say that I've become jaded to describe how I feel about the pun now, but is there a word to describe the original impact?
Edit: To clarify, I'm not referring to the fact that the pun wouldn't have been funny unless I understood it, like with an inside joke. I'm looking for a word to describe a concept that is perceived as being novel lending it's novelty to an otherwise uninspired joke or statement which references it.
Edit 2: A better example would be a remark about a current event. For example, if I was to watch a current episode of the Daily Show, it would be funnier now than it would a year from now even if I clearly remembered the news items that were being satirized. The jokes are funnier because I find the topics, which are not funny per se, interesting.
Edit 3: Another way of saying this would be a joke that is funny because it aligns with my interests. In the original example, students who were in the same class but found math boring would have found the pun boring, even though they understood it just as well.