First, he learned to say "ba ba!" while waving to people and we melted at the adorableness. Then, he learned to say "uh-oh" and we giggled at how precious it was. Next, he learned to say "ah-duh!" (all done) and we rejoiced that he could communicate that concept. Finally, he learned to scream "Na na na na na!" (no!) at the top of his lungs and we covered our smirks and tried to teach him to use an inside voice.
I think he's officially a toddler now: he has learned the word "no", knows how to use it, and won't take "no" for an answer. I think I'll keep living in denial and keep calling him "my baby."