In the beginning, Charlie didn't really have a clear sense of humor. I noticed though that whenever I would laugh, he would sneak a peek at my face and then start laughing too.
Now he totally has a sense of humor, and it's very similar to his parents. Corny as can be. I love it... I guess the apple doesn't fall far from the tree.
Is your LO developing a sense of humor? Is it similar to yours and your SO's?