- Axe Cop is made of this. Axe Cop eats only cake and thinks that girls are dumb. Justified in the fact that the comic was written by a five year old.
- Ethan in Ctrl+Alt+Del. With hints of Psychopathic Man Child.
- T-Rex, the protagonist of Dinosaur Comics, is a Ditzy Genius Man Child.
- Dominic Deegan's brother Gregory has a few elements on this to him. He's old enough to hold a job and have relationships, but he still likes making couch forts, gets pouty after arguments and gets squicked out easily when talking about sex. Normally, he's more "man" than "child", but this did end up biting him in the butt in the later half of the "Snowsong" arc, when he essentially went Off the Rails from Dominic's plan to redeem Snowsong to live out his superhero fantasies when he was a kid. His girlfriend Pam is understandably furious that he unknowingly endangered the town for what was basically a game of make-believe, stressing their relationship to the point that she later broke up with him.
- There are a few of these traits in Kamina in DOUBLE K. Quoth captainosaka:i like how kamina's plan seems to suggest that he's regressing back to the mental state of a vindictive third grader under all this duress
though you could probably argue that he never grew out of it to begin with
- Clubs Deuce/Courtyard Droll from Homestuck has an extremely childish view of the world that borders on Ambiguous Disorder. Word of God says he basically thinks of his fellow gangsters as his goofy family, apparently being completely unaware of what a gangster is (granted the Midnight Crew are kind of losers).
- Parodied in the last issue of Mac Hall. Ian recalls this phrase as he moves into his post-college life (and segues into Three Panel Soul, Mac Hall's Spiritual Successor), but adds the rider, "But I unpacked most of them when I got there."
- C. S. Lewis, in a similar spirit, once said "When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up".
- Amical from morphE. He may be the head of a business with a mansion full of guards. He may be intimidating when he's waving a gun around and forcing people to fight to the death. But if you call him out on being vile or don't let him get his way then he'll start crying and whining that everyone is mean to him and that he works so hard to please and gets no respect. It's as childish as it is manipulative.
- The Order of the Stick has two prominent examples:
- Among the good guys, we have Elan, the dim-witted and silly bard who plays with a clown hand puppet that he worships as a deity. Character Development has helped him along the wait and his childlike sense of purity endears him to the group as The Heart. As for Banjo the Clown? His belief in said puppet is genuine enough that Banjo does count as a very minor god (and was even offered the chance to join the Northern Pantheon by Odin.)
- Among the bad guys, Thog, the even dumber half-orc barbarian who likes puppies and still believes Girls Have Cooties. Despite this, he also counts as as a Psychopathic Manchild since he still loves to indulge in violence and murder. At one point, ice cream was all that was keeping him from indulging in boredom-induced rampages.
- The Monster in the Darkness may or may not count. Yes they carry around a frilly pink umbrella, loves having tea party and overall acts like a child, we don't know their species or age, so they could actually be a child by their species standards. Word of God has compared him to being like a 12-year-old, so he may just be an immature pre-teen (though he also has complex thoughts and opinions... and watched dwarf porn.)
- David Walkerton invokes this trope in order to avoid responsibility (and also partially due to a traumatic childhood event) and can actually be mature and insightful when the situation calls for it. However, even when the need for the facade ends along with the main plot, he continues to act the part, so it's also a legitimate part of his personality as well.
- Joyce qualifies as well; though she's generally more responsible than him she shares his fascination with cartoons, burps, and fast food as well as his goofy demeanor. It's part of what makes them so perfect for each other.
- Not to mention Robin, especially later in Shortpacked!
- xkcd has at least one strip about this.
- Stand Still, Stay Silent: Tuuri and Reynir zig-zag this due to taking turns at acting immature for their age. By default, Tuuri is the one acting like an adult due to having a job on the crew, while Reynir is in a position that makes him The Baby of the Bunch. However, Tuuri also has a huge blind spot about the dangerousness of the Forbidden Zone the crew is exploring and approaches it with child-like wonder, while Reynir takes those same dangers seriously enough to be much more cautious than her.
Man Child / Webcomics