Who is Lucifer?

The other morning we were reading scriptures and we came to a part where the started talking about Lucifer. I stopped reading and asked the kids if they knew who Lucifer was. J in her sweetest most innocent voice said, "You know Lucifer from Cinderella, the cat?" It was so adorable. Then we had to explain which Lucifer we were talking about and who he was. I wish the only Lucifer was the one from Cinderella!