Reading at 21 months?

Timothy can officially read his first sightword. How on Earth, you might ask, can you tell that a toddler can actually read a word? Well, we were as suprised as anyone who might be reading this. We have a book we made for Timothy that has pictures of most of his relatives. It has the name of the person on a big white piece of paper and then below that it has a picture of the person. It starts with himself, which hillariously, when you ask him who he's looking at... he says "you." Because we always say "who is that? It's you isn't it?" So we're trying to teach him to call himself Timothy instead of "you" when he reads that book. Kinda funny.
The next pictures are of us (mommy and daddy). Then Jake and Chayse the dogs. After that, there is a page that says "poppy" but no picture because we have not yet printed a picture for my dad. Following that page are several more blank pages for Grammy, Grandma, Grandpa, Glenn, Jenn, Travis, Ashley, and Ava because we have not yet printed pictures for them either. Yesterday, when Allan was reading this book to him and he got to the page that said "poppy," he said "poppy!" We thought he must just have the order of the book memorized and knew that after Chayse was poppy. But, later on during the same day, Allan flipped straight to the page that said "poppy" but had no picture of poppy and he said "poppy." Our only conclusion from this experience is that Timothy can recognize the word and knows that it says poppy, thus making it his first sightword.