I once got the “Hello Darkness My Old Chum” achievement, which you get by befriending the Grim Reaper. I don’t remember which Sim befriended him, but I’m pretty sure whoever it was had a positive reputation and the Incredibly Friendly reward trait so that befriending others happens incredibly fast.
I got a good screenshot in Sims 3 once, of the Grim Reaper in my Sims’ swimming pool. He showed up quite a bit because zombies would spawn on a full moon and they’d often be Elders, and would subsequently die on my family’s lot. The best occasion, though, was when a member of the paparazzi died on my Sim’s doorstep, only for her (my Sim, not the dead paparazzi of course) to go into labour! It was quite funny having the Grim Reaper freaking out over it. This again was Sims 3.