Da, da, da, da... the Christmas song miracle

Today, I was in the kitchen and I heard a nice song...
Spencer said, "Da, da, da, da, daaa..." It was repeated several different ways, resembling several different Christmas songs. Nothing too spectacular for a 5 year old, but it's what I heard next that amazed me...
"Da, da, da, da, daaa..." It wasn't exact, but sounded very similar. What's so amazing, you might ask? It was my not quite 8 month old baby who said that. She was copying her brother, almost exactly. I was so excited that I ran in and picked her up. I started saying, "Say da-da-da." Followed by "da-da-da." She is quite vocal, has been forever, but this was the first time she copied deliberately. She's been saying that all day. Now we just need her to recognize the connection between saying "da-da" and actually referencing her favorite person. That will take a little while, but for now, I'm so excited!!