You haven't realized this yet, but I don't know everything. There are questions you're going to ask me that I won't know the answers to — especially if you start asking about Disney movies. I don't have all the answers. No one does. In fact, people who are experts in their fields of study don't even have all of the answers to the questions about their field of study.
And that's okay.
It's okay to not know. If someone asks you a question and you don't know the answer, it's okay to say, "I don't know." There is no shame in not knowing. We all must learn everything we know for the first time. Until we learn it, we don't know and there's nothing wrong with that.
There is a responsibility that comes with saying, "I don't know." Once you say it, you've now discovered a hole in your knowledge. It's up to you to fill it. It's your job to find out the answer — if there is one. Ignorance can be excused once, but not multiple times. Don't be intellectually lazy. When you have to say, "I don't know," that should be your cue to leap into action and do some learning. Of course, there are some exceptions to this. If someone asks you what you want to be when you grow up, you can answer "I don't know" until you're, oh I don't know, 40. By then you should probably have a pretty good idea. Until then, feel free to say, "I don't know" if you really don't know.
Don't abuse it, though. Whenever you're about to say, "I don't know," remember that those three words are a great way to start a conversation where you and the other person (or group of people) end up learning something new by the end. "I don't know" should never be an ending but always a beginning.
P.S. — If you've ever wondered why your stuffed animals seem to move around your room while you are sleeping, don't ask me. I don't know.