It's a community where the "rule" is that you post before you leave, and your post title must contain the word rule. Basically it's just random silly images and because there's no set theme for content, it has a low barrier to entry. That's why you're probably seeing a lot of it.

It's a 20 amp breaker.

https://en.wikipedia.org/wiki/Carry_On_(novel)

That's not what this is though. You aren't emphasizing how "after" it was. You aren't distinguishing it from some sort of "before-after". This is just a typo.