Ah, I can totally relate! My ds is 3.5. He too is incredibly smart, verbal, and funny. He loves words, loves to make rhymes, say silly things, etc. He is very loving and sweet. He told me (without coaching) that he wanted to get me flowers and chocolate for my birthday. He'll come up, rest his head on my shoulder, and say, "Mom... you da best!" He has more energy that I'd ever dream of having. When I ask him where he gets all that energy, he tells me, "If you want energy, you have to be silly like me! You have to hide from Daddy!"
However, "mouthy" is the name of the game at our house. I honestly don't know where he comes up with some of the stuff he says, since we never say things like that to him. His latest, hissed with as much venom as he can muster during a tantrum, is "You're a BAD mom!!!" He doesn't tantrum as often as he used to, but when he does, look out. He has a very intense temper and his first impulse is to lash out both verbally and physically. We STILL have problems with him hitting and kicking us when he's angry. (He doesn't do this to other children, just to mom and dad.)
My ds also wants to be both "big" and "little". Actually, the being little part is driving me nuts, especially when it comes to getting dressed. I know he is perfectly capable of dressing himself, because last fall he went through a stage where he wouldn't let us help him at all. But now he will not do any of it by himself (most of the time). I have to negotiate all over the place to even get him to put on one of his shoes. He tells me that it is too hard and he can't do it. He also still asks me to carry him a lot. Part of me wants to honor his need to be "little", and part of me worries that I am promoting dependence by not encouraging him to do these things himself. He also talks in baby talk sometimes, and that can be really annoying. How come they want to be big when it's something they can't do, and they want to be little when it's something they're perfectly capable of doing? Maybe it's the process of trying something challenging that makes them feel big, and then when they can do it easily, they can relax more to enjoy the attention and support from parents?