Alright this topic is one I have alot of experience with. Like, alot.
Ok, so, a bit of context here: I'm 37. But I'm DEFINITELY on the childish side. Even people I barely know or just met will always refer to me as a "kid". Not quite sure why, but they're not exactly missing the mark. Even my appearance isnt quite right, for someone my age (apparently). But there's a couple of photos I want to show here, just to make a point:
View attachment 57368
This is the top of my dresser. As you can probably guess, I'm a gamer, so it's all game related stuff. Aside from that starfish anyway, that's not from a game, it's just dead.
View attachment 57370
And that's my desk downstairs, currently set up for a solo playthrough of Spirit Island, a board game (many these days are playable solo, so that's what I do, I have alot of them). That big monolith with the freaky red light is my main PC, and the "VR zone" is behind me, that's what those tall things are for.
You can probably spot a bit of a theme here. If you were to wander around my other "areas" of the house, they're much the same. You'd find lots of twisty puzzles, drones / quadcopters, and every conceivable Minecraft-related object you could think of. I'm also really into cosplay.... that's what the green and yellow thing in that drawer in the first photo is for.
Yeah. I'm about as childish as it gets. I am fully aware of this. Heck, you should see how I am around my dog (or any dog, or any cat). Around him, I ignore everyone else, and get down on the floor with him, so I'm not towering over him. I'll often then make alot of very high-pitched noises, because for some reason he likes that (heck if I know why, dogs are strange). Would that look silly to most "adults"? Sure. Do I care whatsoever? Not remotely.
And like you, I'm familiar with alot of "kids" stuff. Heck, freaking Pokemon, right on that dresser there. And if a show looks entertaining and whatever? I couldnt give less of a crap that said show is intended for 8-year olds. If I like it... I like it. It really is that simple. Also, yes, I've had alot of stuffed animals over the years, ever since I was little. It got to the point where I cant sleep unless I have my arm wrapped around something (which these days is this misshapen, smashed up pillow). As you have said, all of this stuff "feels natural".
And here's the thing: There's nothing wrong with any of that. Yes, some parts of society will say otherwise. Those parts are bloody stupid.
Alot of people out there spend so much time trying very hard to be something that, deep down, they really arent. And then later on, they end up wondering why they're so depressed and sad all the time.
But I say... why bother? If you are a certain way, just go ahead and BE that way. You like childish stuff? Kid's shows, toys? Hey, great. That's super. Or maybe someone is the sort of person that lives and breathes football and screams when their favorite team scores? Hey, great. That's super too. Whatever.
It's alot more important to be yourself, rather than to try to be what others tell you to be. PARTICULARLY for us on the spectrum here.
And you know what, there's a certain way I've always looked at this. I always say "normal is boring, at least weird and strange are actually interesting", and that's my genuine outlook on stuff like this. Sure, I'm strange, I'm aware of that.... but holy heck am I glad I'm not "normal". How fantastically DULL that would be. I'm surrounded by "normal" adults. They could put a concussed chicken to sleep, they're so boring.
But there's another aspect: I think you'll find... if you look around... there are alot more people like you than you think there are. And they might REALLY get into the stuff you're into. I mentioned things like board gaming and cosplay, right? For board gaming, I know people who are in their 50s or 60s who are REALLY into it, some of them purely playing solo even... these people will have entire WALLS of games (whereas I only just started my own collection). There are ALOT of people like that, it turns out. And for the cosplay? Entire giant conventions of people acting as bizarre as can get, dressed up as.... anything. Absolutely anything. It's like a festival of geeks. And in meeting people at those events, I find that by far the vast majority of them have the same childish qualities I do, even outside of the conventions.
In other words... instead of trying to follow the lead of people nothing like you, why not try looking elsewhere? You can absolutely find groups of people... who are not kids... that are really into things like kids' shows or toys or whatever. Heck, I used to know someone that was into toys of all sorts. Like, REALLY into them. The guy could have put together a freaking warehouse with all those things. And what's wrong with that?
And there's one thing I want to end this post with, which is the concept of maturity. People have alot of ideas as to what that means.
To me, it means the ability to BE YOURSELF. All that stuff I do, all the games and cosplay and whatever? I'm a mature adult... I can make my own bloody decisions. If I want to sit here and play Pokemon as my hobby, I'll freaking do that. If I want to collect toys, I'll freaking do that. REAL maturity isnt about just following the herd. It's about understanding that YOU make the choices now... someone else doesnt make them FOR you.
It's just too bad that so many people out there cant grasp that.
There, I'm done ranting.