I associate my childhood with embarrassing actions and derpiness. So I guess he does pop up behind me sometimes to do a little crazy FlAIL dancing in front of a girl I'm trying to impress or whatever.
That being said, I do not associate what is generally viewed as "childish behavior" with my childhood. I consider them a part of my unaging imagination, so that has largely stuck around, in the shape of my impulsiveness, my...well childish imagination, and my willingness to re-enact that at will. Also my willingness to wear an MLP shirt, as you outlined.
That has nothing to do with being childish in my opinion, not that that's a bad thing or wahtever.