Medic!

"Medic!" from Final Night #3 (DC, 1996) by Karl Kesel, Stuart Immonen and Jose Marzan Jr.

Another crossover event, this one caused by a Sun-Eater trying to eat our sun. It's the kind of global crisis that SHOULD get all our heroes (and even our villains, as Luthor proves) involved because it's directly affecting our environment. No "call" from above like in other Crises, just a real disaster to deal with wherever you're actually based. What it most reminded me of is the month the Cask of Ancient Winters was opened in Thor and it was snowing all across the Marvel Universe. Today, that would be its own book, with tons of spin-off and tie-ins as everyone tried to make a buck off the Norse disaster. Back in the day, it was just good old-fashioned shared universe logic.

Did I say Sun-Eater? Yeah, that's why we have a Ferro Lad in the 20th century. Of all the luck.

Final Night was also responsible for letting Hal Jordan as Parallax sacrifice himself after becoming an unsuable character in Zero Hour. It's also when Morrison's Justice League came together, though I wouldn't call that a direct consequence.