Putting letter sounds together all by himself!

This morning Ryder and I were talking about letters and he said, "And M for Mommy. And T For Tobi (I think I told him that like two weeks ago). And B for Bookie." Now, the cat's name is Wookie, though he does pronounce it Bookie since he can't quite get the W sound in that word. But the part that impressed me was that he put the letter sounds together all on his own. I certainly didn't tell him that Wookie started with B, since it doesn't. He thought in his head that her name is Bookie and Bookie starts with Bbbb and that's the letter B. Like I said, I was quite impressed since this is the first time he's ever done that!