And then I took the wrong exit

I've noted before that my favorite punchline on Tumblr is "hang on, gotta look something up/okay that's funny."

Let me explain why:

It is a way to say "I don't get it" without blaming the joke or the teller.

It is a tacit admission of ignorance without shame or judgement.

It assumes responsibility for acquiring the knowledge the respondent doesn't already have.

It cues other people who Don't Get It to do the look-up themselves, allowing them to get that full impact of Getting It without derailing the post with explanations.

It gives subsequent readers, whether or not THEY got the joke, a little frisson of good feelings when they realize that someone else is now In On The Joke.

A Glasgow building during demolition (1972), showing soot trails to chimneys.