Seemed he had a lot of fun making them movies. Smokey and The Bandit with Jackie Gleason was a real hoot. I can't remember off hand, but he was offered and turned down a lot of roles in a lot of successful films back in the day. Maybe Hans Solo in Star Wars?...quite a few others as well. I kind of want to say "Sonny" in The Godfather, but that's probably not right.
There's a recent movie about an old has-been actor who a bunch of frat boys haul off to a supposed honor function, old actor thinks it's going to be a big deal, turns out it's just a film school frat house party of sorts. Something like that. Shenanigans ensue....or sadness in the realization that the last act is being played out and the final curtain call beckons. I booked marked it, might be as good a time as any to take a look. I think it was rated to not suck.
He was sharp right up until the end. No alzheimer's. I was just watching some old Burt w/ Johnny Carson Tonight Show appearances, and more recent Burt interviews a couple of weeks ago. He looked old and frail, but was definitely still there mentally.
RIP