So I started a fic, recently, that
starts out with Green Lantern (Hal, in case that matters) contacting Batman to alert him that a dimensional tear was detected in Gotham City.
Only...is Green Lantern really the best character to have alert Batman of this? I mean, I have to admit, the main reason I went with Green Lantern is because I couldn't think of anyone else. Is there a character better suited to contact Batman and go "hey, a dimensional bleedthrough's been detected [by who?????? with what??????? past-writer-me sure was merrily unspecific] in Gotham City; maybe you should look at these coordinates since you're already there"?
I mean, an obvious choice among "characters who would notice if a hole in the multiverse suddenly opened up and deposited something and then closed up again" would be the Monitors, natch (or just the one Monitor, depending on your continuity). But I kind of doubt the Monitor has Bat's cellphone number.