Okay, I'm not exactly sure how "immature" they are, but I do still have several behaviors held over from my time as a child. I think of them like sharks; they worked so well from the start that there was no need to change them, even to this day.
1. I hate dressing up. My preferred wardrobe consists mainly of t-shirts, cargo pants, and flannel shirts. (What can I say, I grew up in the Nineties.) I really like flannel shirts. I plan to get some custom made with my family Tartan as the pattern, and right now I have several sets of flannel bedsheets. If I have to look professional for some reason, I'll wear a dress shirt, but I refuse to tuck it in.
2. I name things. I am a compulsive namer. I play Magic: The Gathering, and all my decks have names based on obscure jokes that only I get. I also have nicknames for many of my favorite cards. For example, I refer to Hellhole Rats [http://gatherer.wizards.com/pages/card/Discussion.aspx?multiverseid=97100] as the Warm Fuzzies. (Go on, click the link. You'll get it.)
3. I also tend to sort things. I once caught strange looks during snacktime at Elementary school for sorting out my fruit snacks by shape and color before I ate them. This behavior also applies to Skittles, M&Ms, and Magic cards.
4. When I was a kid, I was a fussy eater (read: big pain in the ass). My parents were thus forced to institute a "Two Bite Rule", meaning that if I was unsure about some new food item they had foisted on me, I had to eat at least two bites of it so that I could say I gave it a try before not eating any more. As it turns out, a lot of things that look gross actually taste pretty good, and the rule worked out so well that I adopted it and even adapted it for use in other areas. An example would be back when I still bought CDs. If I was unfamiliar with a new CD, I had to hear at least two songs from it before I bought it, to make sure I didn't just want one song, and end up spending $10+ on a CD I hated.
5. I prefer sweets to anything else, foodwise. The main reason I don't drink is because of the taste, and to date the only alcoholic drink I liked was rum and coke. As a corollary, I like the root beer that comes in the glass bottles best of all, and I only buy it for special occasions.
6. I still like the ending where the plucky underdog gets the girl. Wall-E made me cry like a baby.
7. I am somewhat scared of the dark, though only in the places that are completely devoid of light. I didn't really have this in my childhood, and in fact I have The Grudge to thank for it. On a similar note, old-fashioned dolls scare me.
8. And finally, I still make efforts to avoid stepping on those lines between tiles or squares or what have you on the floor. Not sure I'll ever outgrow that one, really.
