Moby-Dick, the great white whale, was a fictional character created by writer Herman Melville in his book of the same name, originally published 1851.
During his lifetime Moby-Dick was constantly being hunted by Captain Ahab, one of who's legs had been bitten off by the great white whale. But after their passing, both Ahab and Moby-Dick ended up as ghosts, living together forever on the Phantom Prison Planet. Over the course of 600 years together, Ahab set aside his grudge and began to see the great white whale as his best, and only friend.
The two of them were inseparable until the villainous ghost pirate Harpoon hatched a scheme to use Moby-Dick in his scemes to plunder space faring luxury cruisers. First, Harpoon had to seperate Ahab from the whale, by capturing him and holding him in chains on the Phamtom Prison Planet.
Luckily, Futura, Jessica Wray and Time Hopper managed to rescue Ahab by allowing themselves to be taken captive and brought to the place Ahab was being kept. Together they sought out Moby-Dick to help the Ghostbusters free the great white whale from Harpoon.
The Ghost of Moby-Dick first appeared in the episode The White Whale.