It seems strange to me that I've read two picture books in the last month about animal ghosts in lighthouses.
Eve Bunting's Ghost Cat is about a little ghost cat who chose to stay on Earth as a ghost with her owner, the lighthouse keeper. The ghost cat can choose to be visible or invisible and is quite playful with visitors. The ghost cat even manages to save the day one stormy night when her owner can't light the beacon.
In contrast to Bunting's book, Goldfish Ghost by Lemony Snicket, has some darker humor. For example, all of the fish and sea animal ghosts float upside down in the air over water.
He eventually finds a friend who "lives" at the lighthouse.
Of the two books, I think I liked Bunting's better. The story is sweet and I'm a bit nostalgic for my Bloo-kitty still, but the books are both great, with wonderful illustrations.