Apart from author being obviously inspired by the song I admit I don't see any connection or anything worth naming that "the pun." Maybe it's just me.

Making a phone call is an asynchronous event, and as the song suggests, sometimes you give someone your number but they never call back. With any distributed system in real world conditions, a similar situation arises where a request doesn't get handled or is lost along the way.

</explainer>

So he uses the phrase instead of "distributed systems?" (shrug)

It's explained at the top of the original post: https://aphyr.com/posts/281-call-me-maybe-carly-rae-jepsen-a...