I assume they are not ghosts. Does it mean they have come or they arrive?
I think the correct translation should be " they showed up"
Yes. It means they have showed up (they have arrived and I can see them).
"They show up" is an accepted answer as well, just tested it, cheers.
Why not "they've appeared"?
I tried to replace the word "appear" with the sysnonym "turn out" and the app considered it wrong!!!