DC's Green Lantern concept has produced some unique, hilarious and fascinating characters, as the Corps accepts any sentient being capable of possessing will, including a sentient virus, a mathematical equation, and an alien which just so happens to be identical to a squirrel. In one possible future, however, the emerald guardian assigned to Earth is literally a whale.
The Last Days of Animal Man (written by the legendary Gerry Conway with art from Chris Batista) tells the story of an older Buddy Baker who finds that his powers are beginning to fade in 2024. After fighting the super-strong Bloodrage, the stuntman-turned-hero is thrown above the city just as he realizes that he can no longer fly. While plummeting towards the ground, he is saved from a brutal fate by the Earth's new Green Lantern - a 100ft blue whale - who makes a kelp-like light construct to cushion his fall. The citizens of San Diego are apparently unfazed by his appearance, implying that the 200-ton marine mammal is a well-recognized and respected hero in this potential future - and a leading member of the Justice League/Teen Titans merger, the League of Titans!
Equipped with one of the universe's most powerful weapons, this Green Lantern is both brutal and deeply empathetic. After saving Animal Man from falling, he creates a bubble around Bloodrage's head to cut off his oxygen supply, and later consoles Buddy. Although returning in the story's concluding issue to invite Animal Man into the League of Titans, this Green Lantern has not appeared since, no doubt because this possible future ceased to exist after Flashpoint reset the DC Multiverse two years later. Nevertheless, his short but memorable appearance will no doubt raise some questions: why was a whale even chosen as Hal, John, Guy and Kyle's successor, and how do humans feel about being protected by a giant marine mammal?
Although this whale is the first known non-human Green Lantern from Earth, this is not the first time an animal has received a Power Ring: one of the most terrifying members of the Red Lantern Corps is Dex-Starr, a cat (formerly known as Dexter) who was granted the crimson power of rage after witnessing the murder of his owner. Perhaps this Green Lantern was also recruited after showing great willpower in face of abuse by humans, whether extinction by whalers, noise or plastic pollution, or forced migration due to rising sea levels - or maybe the King of Atlantis himself just put in a good word with Hal.
However he came to inherit the emerald light of Oa, Conway and Batista's unlikely marine hero made a welcome addition to the ever-expanding DC Universe in his short but memorable appearance. With all past continuities brought back into canon by the recent Infinite Frontier era, it's possible that Earth's future protector could return to protect the planet and perhaps teach humans a little humility as they're watched over by a decidedly non-human Green Lantern.