Okay, yes, I do understand the plot. Cindy couldn’t catch the ball; or it went nowhere near her, and right for one of the houses in the background. And now Moose is on the hook to repair it.
But are we expected to believe his batting sent it all the way over to those houses? Also, isn’t 9×16 kinda small for a window? Also, if they have modern modular windows, is it even possible to replace just the glass as a DIY project?
All right, done quibbling. Your turn.
Comics I Don't Understand 
Bob Weber started “Moose” nearly six decades ago; he retired the strip in April 2020, six months before he died. There is no way to tell when this re-run was drawn, but it’s not at all surprising that an author of his generation would refer to small panes that were once commonly installed in an old style lattice of four (or six) panes to a window (or door).
Whatever with the dates, it remains a pretty weak comic.
@ Danny (2) – You have to consider the target audience. This strip is very similar to “Slylock Fox“, which is produced by his son, Bob Weber Jr., and has a very similar (primitive) drawing style.
Given the barrel of nails in the hardware store, yeah, I’d say this strip is set sometime well in the past, whether or not it was drawn then.
Primitive, eh. Here’s one Weber did for the Comics Curmudgeon:
For some reason, the image didn’t post. I’ll try again in case it was an error on my part.
Here is Jeff Stahler‘s approach to the situation:
I’m afraid there’s a very disturbing ‘urban slang’ meaning of “pop one out”.
Is it just/predominantly UK, so the cartoonist doesn’t know?
I was wondering if there might be, and was hesitant about using the phrase in the post title.
@ MikeP (8) – Both of the “Bob Weber” comic strips maintain a clueless (slightly archaic) innocence that has absolutely no connection to (nor awareness of) that kind of crude modern slang.
P.S. British readers may be amused that in American baseball parlance, the fielders (like Cindy in this comic) who catch and return balls during batting practice are said to be “shagging” fly balls.
Hope she doesn’t fall on her fanny while doing it.
I don’t think it is just a UK thing as I know the meaning (or at least a meaning) otherwise and don’t associate it with UK.
There is a US version of “fanny”, meaning the buttocks. The UK means something on the other side.