What does it mean when a long-time male friend acts this way?

I have a friend that I've known for nearly 16 years. We've always been fairly close and able to talk about anything and everything. A handful of years ago I went to see him and he acted really different. Rubbed my thigh, slapped my butt, complimented everything from my hair to my accessories, made passes that others noticed and commented on, and I woke up to him rubbing my arm. One night I went to the couch in the middle of the night and the next morning he asked why I slept there and said he "kinda thought I'd sleep in his bed with him." He even asked me to an event with him and we had a lot of fun. I tried bringing it up and he got a bit weird about it and we just acted like it never happened. We're still close, and he tells me I can confide in him and that he understands me. I'm just confused. Why would he suddenly start being this way? I'm honestly not sure what I think, I guess I've never really thought about it until that point. Is this just being friendly or what's up with this?

What does it mean when a long-time male friend acts this way?
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