Last night, Jason was reading the kids a counting book. He started counting, "One, two, three..." After a couple pages, Vivienne started saying "two" with him, and she even said "three" before him once. After that, she just said "two" and "three" with him. I doubt that she really has any concept of counting things yet, but it was cute that she was able to copy him and anticipate the next number.
I tried to catch this on video, but by the time I grabbed the camera, Vivienne had lost interest. Maybe next time.