1. "Oh, really? What interesting things did we do in our dreams? " This kind of reply is light and humorous, and won't make the other person think that you are very stiff.
2. "Haha, it seems that you miss me too much." This reply is also a humorous expression, which can make the other person feel your sense of humor.
3. "I am not the real me in my dream!" This kind of reply can let the other party know that you don't want to make this matter stiff, which has a certain teasing meaning.
In short, no matter how you reply, you should try to be relaxed and natural, and don't let the other person think you are very stiff or embarrassed.