The story cuts away from the main character for several years (and several chapters). When the other character meets up with him again, the main character is heard but not seen during a very serious exposition sequence for several panels. Then he is finally revealed in all his glory.
When Yoshitsune and Yujiki are trying to find clues as to Friend's identity, they need to check a history book and Yoshitsune decides to rummage around Kyoko's bag for one:
Kyoko: "Stop it! Don't look inside a girl's bag like that!" Yoshitsune: "One or two condoms isn't going to shock me."
The scene where the engineer tries to explain the problems with the Friends' Humongous Mecha plan
The guys' horrified reactions to seeing that they included a pornographic movie poster in their time capsule.
In a serious moment Chouno sits at the shrine of his dead grandfather. After a heartfelt talk he resolves to follow in his footsteps and stands up. And promptly falls down. His legs fell asleep.
Poor Kyoko is basically a walking funny moment by virtue of having the worst possible luck a character can have without getting killed. Her facial expressions don't hurt.◊
Yoshitsune hands Kyoko an ID card. The photo used was one he took of her in the bath.
When Kanna and Chouno got to see Father Nitani Chouno sarcastically mentions that he isn't going to ask Kanna on a date. Kanna replies, equally sarcastic, that the line sounds like it came from a romcom. Chouno's expression is priceless.
In the 21th Century boys' climax Kenji is riding his bike rushing to his destination when in a very serious and important moment...then his bikes runs out of gas and he falls off, Kenji was not happy at all.
In the midle of very serious scene Kyoko unwillingly pushes Sadakiyo'sBerserk Button by confusing Tetsujin 28 with Gundam and he starts ranting furiously. Made funnier if you are in Humongous Mecha fandom and know that some people in it can flip off for similiarly silly reasons.