Interesting topic! I want to add a little story which happend >12 years ago, but I remember still like yesterday.
At around 24 (5 years after my highschool exam) an "older guy" in his mid/end 30s on the street said "hello" to me.
I am very bad with names, but I never, ever forget a face so I said: "Dude, who are you". And he: "We graduated from higschool together, I'm XYZ". My answer: "Sorry, I have never seen you before, but you have a familiar voice".
End of story:
Of course I knew him from before. He was my classmate for 9 years. But he went from a boyish redhead into completly sly bald in < 5 years. He looked like another person. And older person for sure, but that wasn't the point, all of us got older. But he looked like somenelse. Totally different facial proportions. Just not himself.
I felt really bad (for him) and that I was so "rude". This really sticks to my mind and also freaked the hell out of my as soon as I noticed the thinning in my hair...