The joke is that they all messed up their hair pretty badly, but none of them noticed it before getting to school. Double so because some of the characters are calling out other characters for their mistake when they they themselves are just as bad or worse.
As for the title, it's making reference to how each of them have an addition part to their hair as either a braid or hair ring. Although in Nagura's case, the braid merely switched sides. :D
Hey Fukuda, you have 3 braids today!EEH!?Ha ha ha, that's so you~I did it when my eyes were tired de arimasu .....Yeah, I sometimes am asleep when I straighten my hair outIs it something you didn't notice on the way over de arimasu...?Can you see in front of you de arimasu?You're like that as well Tamada-dono!Hah hah hah, every one of you is careless huh?Increased PartsOh wow, this is...!