can you be an immature adult?

So apparently going to bed is not gonna happen, so I figured I might as well unload some of my brain here.
Lately I have been thinking a lot about being an adult and being mature. Can one be an adult and still be immature? Or does being an adult, by definition, mean you have to be mature? I don't know. I struggle with this, because I am immature most of the time. When I need to be, I can be a responsible adult. Wait... take that back. Not when I need to be. When I have to be. But most of the time, I am silly and immature. I like to laugh and have fun. I like to do stupid things and usually don't mind looking like an idiot. Like swinging on the swings or spinning around on merry-go-round. That's fun. That's kid stuff, so to me it seems like I am immature. I also fear responsibility and fight it often. I also enjoy being spoiled and having things done for me. And I often take that for granted. I try not to and to voice my appreciation, but probably not enough. So all those thing combined do make me immature. But does that mean that I am not an adult? And are all those things flaws? I know that avoiding responsibility and taking things for granted are big flaws, but I am aware of them. And what is it they say about knowing?? Something about half the battle? So, I go back and forth thinking... I should get rid of all these stuffed animals and silly Hello Kitty things. I need to grow up and start acting my age. I am 31 for crying out loud. What 31 year old sleeps on a Care Bear pillow case and wears a hoodie covered in glittery guitars? Oh. Me. So what to do? Well, the hoodie was white and got a big stain on it while we were camping. Instead of cleaning it, it went in the trash. Don't ever think I'll get rid of my Care Bear pillowcase. Maybe when Chris gives up his Transformers one. I am beginning to think that maybe I do need to grow up in lots of ways. But then again, I am afraid of losing myself in the process. I don't know where that fine line is yet. As I am writing this out, it is becoming more clear. I can have the fun, silly stuff, but I really gotta work on the rest. I gotta learn to be more responsible and step up. I need to pull my weight in the world. I let it spin all around me and enjoy the fruits of others labor. And complain when I have to do anything of my own. I know this makes me seem like I am not a very good person. I haven't always been this way. I have just fallen into this comfort zone lately and I need to pull myself out of it. Act my age. But still use a Hello Kitty toothbrush. This is clearly a bigger issue than "Can you be an immature adult?" I think I've worked some of it out. I think its starting to make sense.