Y'know, one aspect of the new Chara lore that just dropped that strikes me (besides uhhh, all of it lol) is that what we know about Chara for sure just really reinforces over and over again, how they really were a little kid. I know people headcanon them different ages because it makes sense to them or it seems to match their behavior or w/e, but really, 9 is their favorite number?? .... they even have a favorite number that they've discussed (apparently at length)???
Like, look at their sprite (and Frisk's) and then look at Kris'. Literal babies. And so much stuff little idiosyncrasies about them doubles down on them having these very childish likes and habits, like them overfilling their glass ("for efficiency!!!") and proudly toting it around, spilling it everywhere. (And the narrator theory, how excited they get over the toy chest in Home: "Look at all these cool toys!" Honestly, how much they talk/narrate in general?? Kiddo's here to A) chatter about everything they see and B) make fun of you. They're doing the Simpsons' HA HA point and laugh, you just can't hear it.)
Seriously, imagine them standing at the front of a classroom and introducing themself with the little things we know about them: "My name is Chara. I really like reading and drawing and golden flowers, my favorite food is chocolate, and my favorite number is 9."
I think that gets lost sometimes, with how Asriel is very clearly a little kid because of how he acts in the VHS tapes and how serious and eloquent Chara is when we see them at the end of the Murder Fun Times route, it seems like sometimes people think of Chara as much older and more serious than Asriel. I know their in-game lore is dark as shit, but there's so many little things that keep underlining that they're really a little kid who got in way over their head. Like, I seriously doubt they're even in middle school.