Toddler craziness

I have a confession to make. I've been working with kids for about 20 years, and I don't think I understand any more now than I did when I started. If there is one thing I have learned, it's that no matter how much you learn, you'll still never know nearly enough. Isaac keeps throwing me for loops. This past week, my child, who has been the world's best sleeper (We would read a few books, rock for 5 mins, then he would ASK to go lay down in his bed. I know, luckiest parent alive, right?) has all of a sudden decided that he is going to FIGHT going to sleep. A week ago, his bed time was 7:30 to 8 o'clock. This week it's at around 10:30 to 11...and we have had to rock him for the longest time until he falls completely asleep before we can put him down or he cries and pitches a fit. I am really hoping that maybe he is teething, because otherwise, I don't understand what happened at all.
Another thing that has thrown me quite a bit...munchkin has pretty much always called my "Mama". Paul is "Da-dee," so sometimes I would get a "Ma-mee," but for the most part, I'm "Mama". Well, today the child started calling me "Mom". I don't have the slightest where he got this from. No one even refers to me as "Mom" so where did he pick this up? I'll tell ya, those little boogers like to keep you guessing.
On the funnier side, today we were all in the store doing some Christmas shopping. I was looking at something and Paul had Isaac up on his shoulders. All of a sudden, Paul said to me, "What is he doing?" I look up and Isaac has gotten my pen I was writting with, pulled up his shirt, and is drawing all over his stomach. Daddy gave a terrific effort, but he could not get all the pen marks off during the bath. Ah, toddlerhood.