Meeting old friends is a special experience. When you meet people you knew 20 or 30 years ago it is easy to recognise them although their appearance has changed greatly. You could recognise them anywhere. It doesn't have to be a special reunion event. You don't say "you used to be so-and-so", but recognise your old friends to be the same identities as the ones you knew before, although we all have changed.
Friends are important in establishing identity. We become who we are through them. We learn how to handle conflicts as well as how to laugh and cope positively with a tough reality. So with old friends we can immediately laugh and feel comfortable because they are a part of ourselves.
Often we make new friends at times when we are going through major changes in life and learning a lot of new ideas. These friends are special friends and remain with us for life.