Peridot & Tulip
Why do Peridot (Steven Universe) and Tulip look similar? They both have green and black in their design, have eye ware, similar noses and are smart.
I think this is not a coincidence. Gems would most likely need to have infinite memory that stores infinite knowledge to correspond with their infinite life span. Aquamarine said that she had a perfect memory, or an infinite memory.
What if the Infinity Train represents Peridot's mind, and Tulip represents Peridot. In Steven Universe Lapis just left Peridot. Peridot wants to go home, to when she lived with lapis, or when she worked for the Diamonds. Tulip wants to go home.
Wait! What about One-One and the Steward and Corgidia, or the other cars and the hand-number-thing on Tulip's hand! How do they tie into this? you might be screaming at your computer as you read this, or not because normal people don't scream at computers.
One-One represents Peridot's limb enhancers, they helped Peridot, yet she has strange feelings about them. She would feel glad to have them, yet she would also feel sad. They represent a time in her life where she was a robot, following out comands. Could this mean that a purple
The Steward could represents Lapis. They both effected water in their debut episode and that's about it. Although, Tulip seems to fear/dislike the Steward and Peridot did fear/dislike Lapis. (Also please don't make Stewlip a ship.It's just . . . no.)
Corgidia represents Earth. It is abundant in natural resourses and life. Peridot at first wanted nothing to do with Earth, neither did Tulip. Both eventually liked it.
Other cars on the train represent Peridot's mind. We see a bubble car (The Burning Room), a chess car (Peridot's "leadership"), a car with a mechanical puzzle (Peridot's knowladge of machinery and technology) and of course a fart car (Lapis). (I'm not including Corgidia because I already talked (???) about it.)
The hand-number-thing on Tulip's hand could be . . . anything. It does glow green though, so . . . green.