Traditionally, once a boat is named it is bad luck to rename it. Greg and Steven tried to rename the ship from "S.S. Misery to "S.S. Li'l Lappy", which resulted in their bad fortune in the episode.
This episode is only the second time Lapis Lazuli has met Greg, and the first time they've been face to face; the first time they ever met was indirect, in "Ocean Gem" (S01E26), where Lapis tried to fight off the Crystal Gems with copies made of water, broke Greg's leg, and almost succeeded in drowning both Steven and Connie after stealing the ocean to try to escape Earth's gravity.