I wouldn't call my actions, thought-patterns and interests childish, but I suppose other people might, to some degree.
The reason I wouldn't is that I see no evidence of these things being immature in me. But some aren't The Done Thing for adults - according to social norms, mind you, not actual maturity. I don't want to give specific details because I'm active on several forums and don't want to be traced through my illustrious array of unusual intests - any one of which might not raise eyebrows on its own, but together I'm sure they do, occasionally.
To be considered a fully fledged adult, it seems to me you have to accept some trappings and dogma simply as is. There's no reason for why artifically blonde hair is more acceptable than artifically pink hair except social concensus. If one were to say that the pink-haired person only does it for attention - well, first you'd have to be sure that's what they're doing it for (perhaps they just like themselves with pink hair?) and secondly, even if they did it for attention, is that really more immature than the drive towards conformity that has to be suspected behind a vast proportion of the many, many artificial blondes? I remember being asked something about jumping off bridges if everybody else did as a child... the point of that question didn't suddenly lose its validity when I became an adult, and yet suddenly I'm expected to jump off bridges along with everybody else, and no one seems bothered by the non sequitur.
If what you're doing is hurting no one and if it's consensual when it involves other people, then I would forget about what people think of these things, with the one caveat that, if it threatens your job and therefore your income and by extension your existence, you may have to make concessions to what is thought of as social acceptability while you're on the job. That's an unfortunate fact of adult life, but I would work towards not letting it colour my own perception. I'm not saying that you should put up with any and all expectations for the sake of a job, just that I would pick my battles. With the small stuff (things like superficial social custom rather than profounder issues like e.g. sexism, although one can bleed into the other) it has helped me to take the view of an outsider - that of an anthropologist in a foreign culture. Where this breaks down, of course, is the point where you're expected to participate in that foreign culture. But that perspective can still help to internally distance yourself so you don't internalise the cognitive dissonance as something that's wrong with you. Instead, you can simply take the dissonance for what it is and move on. I don't know if that makes sense.
But, I'm under the impression that especially neurotypical people don't choose their interests, thought-patterns and behaviours freely but indeed out of expectation, to a great extent, since many seem very conscious of and concerned about their social prestige and standing. Just my thoughts, but I think that, for that reason, they care more than autistic people do about the fact that they tend to only get away with perhaps one quirk. One can even be good. But it goes downhill from there if you add more. So, for the most part, they don't. And they don't know what to make of it when other people do, because it goes against the central objective of being a person in excellent social standing. Perhaps they conclude that the person who doesn't conform therefore hasn't grokked how to achieve that objective and must therefore be childish. If What Other People Think is a carefully managed and central part of adult life for many neurotypical people, perhaps they don't know what else to call it except childish when they see someone else not doing it.
In spite of all the hype about doing one's own thing, the occasional neurotypical person who also doesn't care so very much about What Other People Think gets under the same fire we do for being 'childish', as I know quite well from acquaintances, and that's how I arrived at the conclusion I mentioned.
You should be proud of yourself for that. Next time this subject comes up, if it does, I'd just tell them that you enjoy having fun & there's nothing wrong with that. Life is too short to be so serious all the time. (Maybe that could be your "comeback"! lol) About girlfriends, you might tell them that you look forward to finding a girl who shares your sense of humor & playfulness - because that would be one pretty great girl!
