My son's vocabulary grows by the day. Don't you wish learning new words was still that much fun? He also tries hard to put new things in known categories. For example, this evening Kristy was reading There's a Wocket in My Pocket to him, and he was trying to classify the Dr. Seuss fantastical animals into things he knew (like "duck" and "dinosaur"). He was quite convinced he was right, too!
In case you're interested, my personal favorite is the nooth grush (on my toothbrush).