If I remember right, there was a guy on WP who had responded to his wife's miscarriage by ignoring her plight and immersing himself in computer games, which either destroyed the relationship or very nearly did. I guess that's an extreme case of childlike expression in AS, and a pretty negative one at that. Less horrifically, I know an Aspie in her 20s who is still collecting small plastic toys by the bucketful, weeps just like a toddler when frustrated (but soon comes to terms with the situation and deals with it), and genuinely seems to need a caregiver to help her navigate through the cruel adult world which bowls her over repeatedly. She thought nothing of walking around a supermarket in a cosplay outfit rather than getting changed. Yet she drives a car competently and does extremely well academically (as long as she's taught in an appropriate way), and she can be very responsible, like the time her exhausted mother was about to regress in public over a "last straw" problem over car tyres at a garage, and the daughter led her away to somewhere quiet so she could recover without making a spectacle of herself.
In my case it's hard for me to know. I've often failed to step in and do the right thing when the people around me are in trouble, if it's not appropriate for me to offer a practical solution, but I've not noticed other people giving each other such help very much either, and I tend to be my own worst critic because of my perfectionism and possibly low self-esteem. I did notice that I only fairly recently began to take much responsibility in relationships, like accepting the rough with the smooth in a mature way.
I really don't know how much my liking for teddy bears and all kinds of silly things reflects my ASD. I once put a small teddy bear in my shirt pocket with his head clearly visible (one I'd rescued from a pile of unwanted junk because I couldn't stand the thought of him going into a landfill), and went out to a public bar like that, but I was performing "The Teddy Bears' Picnic" there as part of the entertainment, so it was artistic license and a promotional stunt. I wouldn't readily display a teddy bear like that in most other social situations, unless there were children to delight, but I can't help feel that I should be allowed to. It's a very blurred issue because I'm a performing musician, and we get away with a lot of wacky behaviour.
I think another reason it's such a blurred issue is that people seem to be lightening up more these days, and accepting that it's OK to be more childlike. I know lots of people who still unashamedly enjoy comics and kids' cartoons, and I think there's many a father who has enjoyed something of a second childhood while parenting his kids. I used to love reading to my young son, it gave me an excuse to read a lot of excellent books I was "too old for." And I've heard that humans are the one species that takes decades to switch from child to adult, and that it's normal for us to actually continue to act like kids in disguised ways......a guy says he's bought a particular car because it has the best engine for the money or whatever, and he quotes technical data to prove it, but the car he's chosen looks remarkably like a rocket ship, and it's full of shiny things inside. How childlike is that?
Clearly a lot of these childlike expression things derive from the Aspie difficulty with understanding what's deemed socially appropriate and the problem of fitting in.