Why would a male co-worker start acting like this?

A co-worker of mine has started acting... weird. We work together daily now since he got moved and his behavior has definitely changed since then. Here's what I've noticed -

*He always finds stuff to talk about with me. Even little, pointless things.
*He has started randomly using my name when he talks to me.
*He looks my way a lot. I will be working and look up to catch him staring right at me. He then typically looks away quickly.
*He turns into "Mr. Funny Guy" when I'm around. He will joke around with people, give male co-workers/friends crap playfully (just your typical male horse play type stuff - nothing bad or mean).
*He makes direct eye contact when we talk and tries to hold/keep my gaze/attention.

A couple recent occurrence examples -

1. He took break with me. Usually, we don't take the same break. He goes before me. I wondered why he wasn't going, then he went when I did.

2. He was working directly with me on something and he walked by me and said "huh?". I didn't know what he meant, so I said "what?" and he was like "Oh, I thought you said something". I said no, I hadn't said anything.

3. Another girl said his name because she had a question. He looked directly at me first. I guess he thought I had said it. I had to tell him SHE wanted him, not me and I hadn't called for him. He didn't pay her much attention at all and kept pretending he couldn't hear what she was saying, so I ended up having to go and see what she needed.

4. I took a day off. He noticed and commented. He told me I had missed all the fun and shared something funny that had happened and commented I wouldn't have had to take a day off because I could have had an "off day" there since we weren't very busy.

Any input on this type of behavior and why he's doing all this?
Why would a male co-worker start acting like this?
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