Every evening at bedtime, I always say, "Matthew, it's time to sleep. Let's give Daddy a kiss." He usually does, right on the cheek.
One evening, I held him close to Bill for the goodnight kiss. Out of the blue, he put one hand on the back of my neck, his other hand on the back of Bill's neck and pushed our heads together for us to give each other a kiss on the lips! He did this a few times much to his delight. I'm sure it was fun for him to be in control by making Bill and I kiss. We never taught him this "trick".
One day, my sweet little boy and I were leaving his auntie's house. I said, "Can you give Auntie a kiss?" then brought him closer to her. All of a sudden, he had one hand behind her neck and one hand behind mine. I pulled away laughing and saying, "Oh, Auntie and I don't kiss like that." Then I think I asked him to wave bye to her instead. He did, with a big smile.