Isn't it strange when you meet someone after a really long time you are surprised by how they appear. Not just how they 'look' but also who they have become as a person. A sea of change has come to pass since your last impression of them. It takes time yet slowly but surely this new image of that person comes to rest itself upon your mind and you forget the old one. Like an OS updating itself in your memory.
And then as time goes by, one fine afternoon, under totally unrelated circumstances, you catch yourself thinking of that person. And by virtue of some glitch in your mind's recollection mechanism you remember him/her as they were all those years ago. And with such vigour that too. You hear their old voice, peculiar speech inflection, their old character tics, the way they used to hold themselves and even the way they used to smell. All those things which you thought time would never change but did in some way.And for a moment you relive that.
And then just like that it fades away.