The reason the ship only had one crewmember
- The ship is absolutely massive, but only the Captain is explicitly mentioned. If there were other crewmembers, they would have had to space themselves as well, right? Well, there are two possible explanations for why such a big ship is so empty:
- The ship has an experimental jump drive. In fact, the insanely long, constantly shifting corridor is the ship's drive. The Captain was taking it for its first test flight, maybe intending to jump to the next system or just to the edge of her home system, and ended up on the edge of existence itself. While she could have used the drive to get back, once she encountered the Not-Things, she knew she absolutely could not let them get their hands on it.
- Or, the ship did have a crew, but they were completely vaporised by the effects of the wormhole. Notice how the cockpit has additional shielding and blast screens. These were in place when the ship fell through the wormhole, saving the Captain's life.
"Mavity" was more than just a gag — it was foreshadowing
"Mavity", more than just a silly running gag, signals that a permanent change has been made to the Doctor Who universe for the time being, due to Donna throwing coffee into the console. While this was small, laughable change, it foreshadows the Doctor using a superstition at the edge of the universe. It's something small, something to get them out of a bind, until the Toymaker comes back in the next episode. And in the Christmas special there are goblins who operate on the logic of luck and coincidence. Not alien goblins. Goblins."Mavity" was foreshadowing a much bigger change to the Whoniverse that occurred in "Wild Blue Yonder", which we will be seeing the ripples of going forward, which would not have occurred without Donna throwing coffee into the console.
