Things like a temporary comet passing by or stars (rarely) going supernova would be very cool to catch one night. I'm not sure how complicated this would be to make but I would for sure love to see this become a thing.

supernovas would mess with constellations if its actual stars - i could just create supernovas out of nowhere, as if a star that was too dim to see by eye exploded (which is reasonable, irl there arent many visible stars that are expected to explode [whoah theres one that just explodes repeatedly, thats cool] any time soon)

meteors and rogue flybys would be cool

perhaps as well as the occasional random meteor, i could also spawn a few comets with a really long period, and then do a meteor shower when they pass by (a sort of innacurate modelling, but yearly meteor showers would be far too common)

That's pretty much what I was thinking, maybe you could add a system that makes a "phantom" star (one that just kind of appears) that is a slightly different colour than the rest, make it last a few nights and that is the one that goes supernova.