@Deathhappens
Hello, certified clown school graduate here. Yes, I was able to get the slapstick joke, I can't say it was funny but ok. What caught my attention was the 4-5 cm comment. It appears that she wanted to make a remark about his penis size. There's where my problem lies.
The set-up was all over the place or rather, there was no set-up at all. We can only see in the last panel that the maker of the slapstick joke has her shoe off and an arrow pointing upwards at her toe. So they want us to assume that her toe was used to measure his dick.
Leaving aside the fact that is impossible to measure a dick with a toe, standing, and with clothes on, We, the audience, couldn't note that the deliverer of the punch line had a clear view of the incident, she was behind their backs, so we can't trust her judgment about Meguru's dick size.
Thank you for your attention.