These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: 20th Century Boys
Big Lipped Alligator Moment: The introduction of Keroyon, where the rest of the group screams at his appearance, followed by a full-page spread of a man with a frog's head. Then he turns out to just be an ugly guy.
The First Friend was responsible for 150,000 deaths by creating a plague and spreading it around the world, also causing widespread death and destruction in order to seize control of the planet and run it with an iron fist where people are sent to nightmarish 'reeducation facilities' or high security prisons just for drawing manga. Friend successfully demonized the heroes and made himself a savior of the world. His whole motivation? Being a massive Attention Whore and egocentric tyrant who wanted to be worshiped by everyone while satisfying a petty grudge against The Hero Kenji
The Second Friend is an Omnicidal ManiacStraw Nihilist who, upon taking over from the first, proceeds to run the world even further into the ground. While the first Friend was a tyrant, the second simply wants to see everything burn. His actions are far more depraved and more and more people are killed under his reign. Even worse, he manufactures a new plague that he sends out with a twist: there is no antidote, only placebos. He simply wants everyone on the planet to die to satisfy his own cruelty.
Crowning Music of Awesome: Kenji's song, Bob Lennon. It's a rare in and out of universe example, as a recorded version was released with the volume it was introduced in. Urasawa Naoki can sing, apparently.
Ear Worm: Kenji's song, Bob Lennon. As mentioned above, it's a rare in and out of universe example, as it plays a very important role in the plot as the story goes on, especially the 'Gutalala Sudalala' version, which even the characters comment on as being an ear worm and since it was released in real life it can end up being stuck in your head very quickly.
It Was His SledThere are two Friends, and the story goes way past the twentieth century. Surprisingly, Friend's identity is a well kept secret.
Hilarious in Hindsight: In one flashback young Kenji and Yukiji argue who makes better sounds - Tetsujin 28 or Giant Robo. In 2004, so very soon after that scene, new adaptation of Tetsujin was released. In which Tetsujin makes the exact same sound as Giant Robo.
Nightmare Retardant: A mob of insane cultists swarming Kenji's shop to kidnap Kanna: Terrifying. A mob of insane cultists swarming Kenji's shop to kidnap Kanna while chanting "DESTINY'S CHILD": a little goofier for western audiences.
Paranoia Fuel: This series is the United Arab Emirates of Paranoia Fuel.