Yeah this happened to me as well. Before I started my Chinese course, I dreamed of the characters '妹妹'. Someone in my dream told me to remember them because this word was going to be extremely important later on in my life. I don't understand how a word could be so important, but I knew exactly what the word was and even said it out loud tonal marks and all. But I guess I could've heard it said before 'mèimei' isn't that uncommon after all.
