Why would a guy act rude with a girl in such ways?

Sorry, this is going to be a along question... But I really need help.

So he is a weird, funny, crazy, creative guy. Everyone says that he's good looking too (I don't have an opinion about that :D), but I like his sense of humor and that... weirdness? But it's not like I have a crush on him, I just like his personality... that he has when he talks to others. Lately in my school our grades where joined together and we started having Art lessons together in small groups of 6-8 people. For some reason he is talking to every girl in my group (there are 4 girls including me, him and this other boy, but he's very shy and he doesn't talk much so I don't think he makes any sense there) but me.

So when he mentions me he talks about me in the third person, like "ask her, I don't know when she's doing this and that blablabla " even though I'm standing right in front of him. Also there was one situation, when he sat with my friend two seats away from me, and my other friend and I sat near the window. He needed to get a brush, and there were few of them on the windowsill so instead of asking me directly to pass one to him, he whispered to my friend something like this "can you tell her (again..her) to pass me a brush). It makes me think that he avoids to use my name and even pretends not know it (?) even though he most definitely does, because he called me by it one time when any needed to borrow a sheet of paper.

So yeah. He ignores me, but then one day completely out of blue he started calling me a funny nickname. (not insulting one, I don't know how to translate it to English). For example, when I walked into the class he shouted "Look who's here, that-nickname". But then the next day it's the same as before - not even a word to me. So that kind of confused me.

I wouldn't care because I thought that he didn't notice me at all, but that change of his behavior from time to time towards me really confuses me. One more thing is that I also thought that he never hears me when I'm talking, but then there was one time when we all sat in class and were drawing. I was talking to my friend and he said one phrase to me that actually showed that he heard everything I said. And during our Theatre classes he always acts stands or sits right in front of me, like completely in front. If you drew a line from my point of standing to his, it would be straight.(sorry for making it so hard to understand). And he whistles the song I like. (I don't think he knows about that but on my Facebook page I've posted that song few weeks ago and then he started whistling it, but I'm the only one from my class he doesn't add to his friends.).I don't even know what to think. Everybody says that he's a friendly guy and so on, but when we are alone, he is so silent and avoids talking to me. I just don't get it.

Does he hate me or something? Because if he does, maybe you could help me and tell me how to befriend him? I don't want to have somebody hating me.
Why would a guy act rude with a girl in such ways?
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