Just watch "Buffy." Giles goes from old guy who needs to lighten up to logical leveled headed guy the youngsters need to listen to depending on what age your watching the show.
My best friend was recently rewatching
Buffy. When the show first aired, she was only a year younger than Buffy herself (the character, not the actress). But when she gave it a rewatch now in her late 30s, she found herself thinking, "Can we forget the teen angst and focus more on the hot librarian?" It was a very odd experience that definitely put age & the passage of time into perspective.
Granted you can't exactly forget what you know so it's not like that knowledge doesn't impact on some level but you know with Kevin Spacey as twisted as this might sound it even kind of helps enhance things because he has played some really twisted people over the years. Of course it can have the opposite effect as well. Norborg isn't quite as likeable in "Police Academy" but then again part of that also has to do I suspect with the fact that O.J wasn't exactly a good actor.
I was just going to say that about Kevin Spacey. I mostly think of him as Lex Luthor in
Superman Returns, so the real life perfidy seems fitting for a genocidal supervillain.
As for O.J., knowing what we know now ironically makes the
Naked Gun movies funnier to me.
As for dead actors, it depends. Back when I was a kid, I always thought it strange that the entire main cast of
I Love Lucy had died before I had even heard of the show. And Mr. Hooper had been long dead by the time I started watching
Sesame Street but they would still occasionally air the old Christmas special, which still has him in it. So I had to process this kind of death of people that I don't actually know from a young age.
I thought it was pretty ghoulish the way that they brought back Carrie Fisher for
Star Wars: The Rise of Skywalker the first time I saw it, although I've gotten used to it upon subsequent rewatches.
I also watch a lot of old movies from the 1930s-'60s and I'm well aware of the fact that most if not all of the actors are dead. Even when I see them give interviews in the bonus features, these are often interviews from 15-20 years ago, so many more have probably passed on by now. That's fine. What tends to hit me is when I learn about actors that died young. Even if they died long before I was born, it's an eerie experience because I've often just discovered them. Like, I recently just for the first time watched
Bells Are Ringing and was then dismayed to hear that Judy Holliday died only 5 years later at the age of 43. It was even worse when I watched
Les Girls and then heard that Kay Kendall died a mere 2 years later at age 32 from a cancer that no one else even told her that she had! Both films are fantastic musicals featuring actors who seem so full of life & energy.
One of the deaths that's unexpectedly hard for me to process is Kellie Waymire. She played Crewman Cutler during the 1st season of
Enterprise. She also guest starred as a quirky zookeeper on
Wonderfalls and that's the thing that always makes me sniffle when I think about it.
Then there's the times when knowing how the actor died retroactively gives new meaning to the thing that they're in. Of course,
The Crow, which is all about death & resurrection, becomes far more poignant knowing that Brandon Lee died while making it.
Then there's all of the
NewsRadio episodes that make jokes about Bill dying or having a mentally unstable girlfriend. There was "Xmas Story," where the Salvation Army Santa in the lobby keeps threatening to kill Bill. Then there was "Halloween," where a psychic predicts the exact date of Bill's death. (She says March 8, 2032. Oh, if only...

) Then there's the elseworlds episodes "Space" & "Sinking Ship," which both end with everyone dying except for Bill & Matthew.