When Arkayna woke up Piper from her bad dream, she was already dressed in her everyday outfit. Considering the fact that Piper was in her pyjamas and was asleep, it would probably make more sense for Arkayna to be in her pyjamas, as it was likely the middle of the night or early morning. For her to be in her everyday clothes, Arkayna would likely have to have been wearing those clothes at that time anyway, or hear Piper having a bad dream and decided that before going to talk to Piper, she should be in her everyday outfit.
Piper's full name is "Pyperia Ashryn Elvanestri", and she was only called Piper when she met Zarya. However, in the first episode, the dragon disk referred to her as Piper.
It's possible that the Dragon Disk announcing the names did not happen in-universe, but was there solely for the audience. In that case, it makes sense, as it could confuse the audience.
In episode 16, Nova Terron shows a clip of the gumlumps in the stronghold. This would suggest that Nova Terron learned of their identities, as the mysticons don't hide their identities in the stronghold. But when Arkayna walked up to Nova Terron, Nova Terron believed that Arkayna was helping him find the mysticons.
Also, Nova Terron said the Mysticons caused the gumlump infestation. Even with assuming the gumlump infestation wouldn't have happened without them, Nova Terron shouldn't have concluded that the Mysticons were responsible, as they were in their civilian forms until the infestation began (Zarya did transform earlier, but even then, it was well on the way). Considering that Nova Terron doesn't know the Mysticon's true identities, he'd have no reason to claim that the mysticons did it, as Piper would just be identified as herself, not a mysticon.
Arkayna having the lightest skin tone makes sense when you consider history and Arkayna's status. In the past, pale skin was a sign of high status, as wealthy people did not have to work outside. With Arkayna being raised as a princess, she would have a high status.
Even after Zarya learns that Emerald's been using Vex-away to control her anger, she doesn't say anything, despite the fact that she noticed Arkayna bossing Emerald around. This seems out of character, since Zarya doesn't shy away from confrontations, so she would have told Arkayna to stop mistreating Emerald. However, considering Zarya gave the advice to tell people she's angry, it's highly possible that Zarya knew standing up for Emerald won't help her confidence, and waited until she stood up for herself.
Piper keeps insisting that her and Zarya are not thieves, even though they are. It's possible that Zarya makes sure that Piper doesn't see herself as a criminal, wanting the young elf to keep her innocence as much as possible.
When Piper tried to fake a monster, Arkayna said they should go anyway, since Piper needs them. It's likely that although she knew the monster was fake, there was a real reason she needed her friends there. She probably thought that by playing along, she would be helping Piper, either by simply being there or being able to learn what Piper really needed.
In episode 10, Zarya says “In common-tongue, please” instead of “in English, please”. This makes sense, considering that Mysticons is inspired by Dungeons and Dragons, and common is a language in dungeons and dragons.
This is also understandable for non D&D fans, as it could be taken as “in a plain way everyone can understand”. This line highlights the D&D influence, while still being accessible to those who don’t play the game.
In episode 7, Zarya said that the sandstorm would shred them to bits, implying that it's dangerous. After the argument, Zarya was left crying while the rest of the Mysticons were leaving the valley. While it is shown that Zarya made it back to the Stronghold, the rest of the Mysticons still left her in a dangerous situation.
