Oh, and going down this route… Matthew Lewis, who played Neville Longbottom in the Harry Potter movies.
Lewis in Philosopher’s Stone
Lewis in Half-Blood Prince
Lewis in 2016
No way! He’s still the same cutie pie I married*, now there’s just more to love!
*may have been a dream
He turns 69 later this year, not 70, but he looks pretty normal for his age.
I have no problem recognizing Diana Rigg, especially when she speaks (although the last thing I saw her in was probably an intro segment for Masterpiece Theater a few years ago). The one I can’t recognize is…
Carrie Fisher
Watching her in the last two Star Wars movies, she just doesn’t trigger any familiarity at all. I think it’s more than just age; her demeanor, the tempo of her voice, just doesn’t look like the same person to me.
I’d say he looks pretty good for someone 15-20 years younger. Hell, I’m 42 and I wish I looked that good! 
Tough crowd, indeed. What kind of septuagenarians do you lot know?
David Vanian Literally did not recognize him last year, even up close, until several songs in. The beard was not a good look for him, but still.
Was gonna go with Iggy Pop or Debbie Harry back before their collagen just up and left them, but they’re also in their 70s and they look like it. Vanian is just 61 and aging very well for a punk.
He looks good, and I’d recognize him, but he is finally starting to look somewhat like an old man. A good-looking old man, but still.
He still looks damned good there to me. I guess I’m horrible with guessing ages, but from that pic, I’d guess 55-ish.
Oh, back to the OP. For me, it was Paul Reiser. I kept seeing him in the credits of Stranger Things and it took me about four or five episodes before I realized who his character was in the show. I kept being like, where is Paul Reiser? Is he not in this episode.
I mean, now that I realize who he is, I can see the facial features, but if I was not told to look out for it, I wouldn’t have made the connection ever. (And even as I was told about it, it took me several episodes to glom onto it.)
I found Billy Crystal unrecognizable the last time I saw him, on Modern Family.
Alec Baldwin. He’s aged well, but just looks so much different.
Good one! My wife and I both knew we knew him but we had to IMDB it to go “ohhhhhh”.
Remember the punk Archie from Repo Man? And the Columbian Drug Lord bad guy from Clear and Present Danger?
Same guy.
For a less cruel comparison, here he is at, IIRC, eighteen (maybe twenty) and here he is last year, age 29. Also, here’s a still from the new X -files.
David Crosby in the mid 1980s was pretty much unrecognizable (except for the smirk) from his days 20 years earlier in the Byrds. But since then he has looked pretty much the same.
The guy from Voyager.
WTH happened to his long, thin face?
https://goo.gl/images/zzHbvQ