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.
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.
In the original manga, the first Friend—Fukubei Hattori— grew up ignored by his classmates, with their attention often focused on hero Kenji Endō. Thus, Fukubei developed a craving for attention, and a disproportionate hatred for Kenji. Already wicked as a child, Fukubei psychologically abused his so-called "best friends," regularly tried to terrify people with his tricks, and ruined the childhood of one of his classmates—who would later become the second Friend thanks in part to the Fukubei's cruelty. Forming the "Friendship Party" as an adult, Fukubei began developing a virus that painfully killed anyone it infected, all while silencing anyone who got his way. Unleashing the virus, Fukubei framed Kenji and his group for the ensuing 150,000 deaths, took over much of the world as a "hero", and ruled it with an iron fist, sending people to reeducation camps for even minor crimes. Fukubei's master plan is then revealed: Use a new virus to wipe out 99% of the human race, then rule over the remaining 1% of "true believers". Sociopathic, egomanical, and petty, Fukubei Hattori set the bar for wickedness in this manga.
The second Friend—Katsumata—grew up unliked and bullied, in particular by Fukubei, and this resulted in a hatred for all humanity. Taking over after Fukubei's death, Katsumata destroys much of human civilization with a new virus and rules what's left even harsher than Fukubei, spreading tales of "aliens" invading to keep innocents terrified in the process. To further cause chaos, Katsumata regularly sends out small doses of vaccines to groups of potential rebels, knowing they will tear themselves apart trying to acquire the antidote. Revealing he plans to destroy all of humanity with an incurable virus, Katsumata tries to make Kenji watch as he kills Kenji's niece, Kanna—Kanna's mother is Kenji's sister, while her father is Fukubei—as revenge for a transgression Kenji committed against him as a child, and, when finally defeated, it is revealed he left an Anti-Proton bomb to be detonated by his followers, which will destroy the entire world when activated. In the alternate Perfect Edition, Katsumata is revealed to have been both Friends all along, having masqueraded as Fukubei and carried out all the initial atrocities himself.
It Was His Sled: There 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, a 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 English-speaking audiences.
Values Dissonance: Friend Land has no trash cans. Instead, guests are supposed to drop their trash on the ground for the janitors to clean up. This is merely strange everywhere else in the world, but it's shocking in Japan, where cleaning up after oneself is a civic duty.
