- Some of Hideo's behavior when he thinks he's alone is...interesting. From the strange dance moves that he busts out in volume 1 to "The Pussy Song" that he frequently sings to calm himself, he's more than a little quirky.
- In the first volume, Tetsuko's behavior while drunk can get rather outlandish, to the point of her urinating in a corner.
- Hideo mistaking Tetsuko's obvious zombification for severe alcohol poisoning would also qualify.
- Mi-chan's post infection obsession with penises, up to fellating a baseball bat someone attempts to use to stop her.
- Hideo and Hiromi riding on a bike with the much smaller Hiromi pedaling while Hideo tells her to hurry up. The two characters laugh about it, but to an extent, this is probably a response to how absurdly awful everything has become.
- Whatever Hiromi actually does to that zombie she mistakes for a giant teddy bear that needs repairs in a feverish delusion brought on by infection is obviously horrifically violent and grotesquely disturbing. We know this from Hideo's reaction, which is confused, disgusted, and hilarious.
- When Hideo and the clearly infected Hiromi get to the top of the outlet mall in Gotemba and are asked to play the "word chain game", Hiromi's first word in most English translations is "TESTICLES". This is very much not an acceptable response, and there's no way that her performance would improve since she is, in fact, infected. Oda manages to rescue her, though, by pointing out that she didn't know the rules.
- After Iura becomes infected and meets Oda on the roof of the Gotemba Outlet Mall, he goes on a long winded rant about learning to control the infection while frantically masturbating. This ends in a panel with Iura holding his severed penis, saying, "Is this immortality?" Easilt one of the best examples of the series' disturbing style of humor mixed with Body Horror.
- Oda waving her urine soaked pants around while standing half naked in the street and scream-laughing is...not a great indicator of mental stability.
- Hideo's obsession with the law can be annoying for others around him at times. He doesn't take out his gun in public early on because of a concern about having it taken, hesitates to steal a car despite the total breakdown of society, attempts to pay for food he loots, and tries to refuse to let Hiromi drink alcohol underage (her sneaking it anyway leads to another moment of hilarity). At least his reluctance to allow others to handle his firearm comes in handy later, and his caution with it manages to avoid making a lot of situations worse. Most of this just makes him awkward.
Funny / I Am a Hero
For a horror series, I Am a Hero definitely has its fair share of humor.