A dream that you are famous can mean that you are looking for recognition. You could be feeling neglected, or you could be feeling that your achievements have not been acknowledged properly.
Dreaming that you are famous can be a message that you should give yourself more credit for your accomplishments. You may have a dream about being famous when you are not feeling very confident.
A dream that you are famous can mean that you need to make yourself stand out more if you want to succeed.
Dreaming that you meet, or that you are friends with a famous person can simply be wish fulfillment, if you are fan of that celebrity in real life. However, a dream about a famous person can be a sign that you admire a quality of that person and that you wish to develop that quality in yourself.
If the celebrity that you dream about is somebody that you do not like, you could be afraid that you are beginning to develop some of their negative qualities.