Mew Berry doesn't appear in a episode, she appears in a sequel manga; the second season to Tokyo Mew Mew. A manga is a book incase you don't know. The manga is called Tokyo Mew Mew A La Mode. There are only 2 books of it so far. Sorry this may be a spoiler but Berry becomes the new leader of the Mew Mews because Ichigo goes to England with Masaya.