By "mean," I don't mean they're always unpleasant. It's just that they're more often than not grumpy or not too sociable. Why is that?
By "funny," I don't mean they're always comedic. It's just that they have stories that are genuinely humorous and observant of something common and quirky among us all.
In both categories, older people can also be "weird." By that, I mean somehow exotic in their interests or behaviors and maneurisms. Maybe that's from spending a lifetime "finding themselves" and figuring out how they want to be. Or maybe not.
Sometimes, older people are very wise. Wisdom is often some combination of all of the above: seriousness and a sense of humor, backed by years of stories and experiences.
I'm most impressed when I meet someone who is really fully mentally present and just sharp as anyone half their age. That is truly the most remarkable and special, and I wonder why. What's their secret? How can I grow up and still be quick and "with it" (I like seeing older people with iPads and knowing more about the latest bands than I do)? Why aren't more people like that naturally? Seeing people like this always inspires me (even though it also creates quite a cognitive dissonance).