Early signs of terrible twos

My office mate's son is two weeks older than Nathan, so we spend quite a bit time exchanging parenting stories. Our conclusion recently is that the "terrible twos" have begun.
Sigh... it's sad but true Nathan is becoming more and more self-centered these days. He's temperamental and harder to please in general. But looking at it from the bright side, I think one reason he's harder to please is because he's getting smarter. All the old tricks that used to work when he was 18months are quickly becoming old. I guess the challenge is on us parents now to look for new ways of keeping him entertained.

Signs of the "terrible twos":

* Throwing tantrums for no reason
Usually when I get home he's all happy and excited to see me, but recently he becomes moody as soon as I set my foot in the door. He will be happily playing with daddy but after seeing me he'll start wining / fake crying. I've read about this in a book once and their theory is that your kids put on their worst behavior to test that your love for them is "unconditional". I sure hope that theory is correct...

* Refuses to get dressed after a bath
He's always enjoyed running around naked, but it's getting harder and harder to get him into his pajamas now. All the bribes/tricks that used to work (e.g. "get dressed and we'll go see the moon") has all stopped working now. These days whatever we say the answer is always "no". Sarah seems be a lot better at getting him to comply in general, but even she admits she has to 连拐带骗. James and I are quickly running out of ideas on how to distract/coerce him.

* Becoming jealous of other kids
Nathan has never shown signs of jealousy before. He's always been a very friendly guys, likes to share his toys, especially his food, and loves it when we have guests over. But recently he got very upset at the park when Sarah starting holding another 10-month old while he was on the swing. He immediately wanted to get off the swing and tried pulling the other kid away.
At home he gets jealous of daddy too sometimes. If James give me a hug he gets upset and tries to squeeze between the two of us. I always thought it was cute but hopefully he will not be like this forever =)

* "No" is the favorite word
Nathan is certainly saying a lot more words now, but on the most frequently used list, "no" is definitely #1. Almost any question we ask, the default answer is almost always "no". Even though he can say "yes" now, the ratio of yes : no uttered is probably 1 : 100.
He often knows what's not allowed/encouraged (such as throwing a toy), but will do it anyway, and say "no" out loud afterward. As if he's telling himself: "Nathan, don't do that."