Transformation

I'm not sure what has taken place in Elijah's little head, but he has gone through a bit of a transformation over the past few months. I'm not sure if it's delayed stress/anxiety over Ella being here, or if he's just ready to be in a school environment with more structure, or if he's going through some weird developmental changes. What I do know is that he seems to have developed this alter-ego thing that comes out every once in a while. Half the time I'm talking to him it's as if he's gone deaf. The other half of the time he looks at me with this mad-man look, crosses his arms and outright defies me. Or he just cries and says that he's so sad. It's almost like he's going through weird emotional hormonal changes which I wasn't really expecting to have to deal with for at least 8 more years or so.
So, I'm curious. I've never really done this, but I'm looking for some feedback and opinions from blog-land out there. He's certainly not out of control or having serious issues with his behavior, and I definitely don't feel like we need a housecall from Nanny 911. I'm just curious about other mom's experiences. So let me know what you think.
It's probably just my first sign of him becoming more and more independent in thought and action. I know he's probably just doing that toddler testing game most of the time, but my job all of a sudden got a lot harder since he expects a logical (in his toddler mind) explanation for every single thing that I tell him to do or not do. And then he'll try to reason with me and explain things his way. I guess I should be thakful that he has such an active and intelligent mind, but to answer his own question to me, "mommy, am I wearing you out?" Yes.