Flying Submarine
An actual flying submarine that started out in the original Party Goers. It belonged to MagiKoopa, but got stolen by Sapphire towards the end of the OG. Then there was two at one point in later OGs, I think, but one of em got blown up. It's really confusing as to which person actually had the still non-blown-up flying submarine, but both people had one, anyway. All in all, it was one of the reasons why MagiKoopa kept trying to write his characters out of the PGs (He held the belief that Sapphire's flying submarine was the one that blew up and she didn't have one). He put up a hell of a fight, though.
Also, if I can remember GORE's addition accurately, the flying submarine became a lot more common vehicle afterward (causing me to suddenly wonder why a space-worthy submarine has never surfaced in any of the Galaxy Goers) and even inspired vehicles such as the Flying Monkey. Because of this, it caused Masa to be the subject of ridicule when he let the others know that his submarine could only go underwater in GMOG Holiday Special: Happy Father's Day Masa!.
The very first flying submarine had been designed by Wizzrobe, who had stolen the blueprints for Leonardo da Vinci's flying machine and double hull. With help from Ruby Red he was able to combine them into a feasible vehicle; before it could be built, however, the designs were stolen by Hrunting. In The Festivity Attenders: Revenge of the T, Hrunting had successfully built a flying submarine out of wood and taken all of the credit for himself. It was easily torn apart by Wizzrobe and SteveT in separate fits of rage.
A flying submarine also appears in Otto McCloaker's possession during A Steam-Powered OG. This variation uses a balloon to keep itself afloat. It was fixed up by Samwise Fitzgerald to be used by the Society of Polite Inquiry in their endeavors against New Lantis, but attacked shortly after leaving Turquoise by Wizzrobe. The submarine survived and was taken to a nearby archipelago, where it washed aground and was abandoned when the Society left three years later.