In “Flight of the Bumblebee”, a very early episode, Oscar doesn’t really understand what Rebecca is saying when she starts using more technical jargon. In a later episode, “Radio Oscar”, he is the only one of the orchestra who immediately is able to understand what she’s saying in more technical jargon. Makes sense after hanging out with Rebecca for a while that he’d have a much better sense of what technical jargon means.
Oscar says in "Flight of the Bumblebee" that he exclusively uses beeswax furniture polish, which he says is the best. This makes a lot of sense when you think about it because he was once the leader of the world’s piano. Even though Thadius hated him, Thadius’ mom would likely want to keep him in good condition for her son.
What counts as music and what doesn’t can seem a little arbitrary. For example, according to the show, percussion instruments make music but door knockers are still used and allowed. Why is this? Well percussion instruments are instruments, so the sounds they make are considered music because Thadius hates musical instruments just as much, if not more than he hates music.
The season 2 episode “Sleeping Beauty” has Oscar tell Rebecca the story of Sleeping Beauty to help her fall back asleep after a nightmare. The story has all the characters replaced with people Rebecca knows, for example Rebecca is the princess, Thadius is the wicked witch, and Oscar is the prince, and the story is changed to be closer to what the orchestra is going through. Oscar’s using the story as a way to tell Rebecca he’ll do everything he can to protect her!
Four episodes later this turns Heartwarming in Hindsight as Oscar saves Rebecca from falling to her death.
In the episode “1812”, Oscar is the only one who immediately realizes the “pictures” being put up all over Old Vienna are targets. Makes sense considering he was once Thadius’ piano and therefore would have a good grasp on how he draws things.
In "The Battle Begins" the orchestra get pushed off Thadius’ balcony and its treated as if they will hit the ground and die, but in the season 2 episode “Carnival of the Animals” Eric falls off the same balcony and simply lands in the river, and due to the soft water property of water in the show had the orchestra landed in the water they would have been fine.
In "The Battle Begins", Mr. Crochet lets Rebecca stay behind in the restaurant by herself to finish cleaning up, despite the fact that he knows there is a dangerous situation going on outside, namely Oscar is being chased by the Zimmerskimmer in the streets. However, Mr. Crochet is shown to be pretty protective and worried about Rebecca in later episodes and even in this one as well, so it’s weird that he let her stay by herself.
In “A Fight at the Opera”, the orchestra is scared Thadius is going to find the Metrodome. But the season 1 episode “Oscar Cracks a Nut” shows that Thadius already knows about the underground tunnels.
The Metrodome might just refer to the room where the Orchestra does their practicing and not the underground tunnels as a whole.
In the first episode during the flashback, Thadius threatens to “lock (Oscar’s) lid and throw away the key” if Oscar doesn’t cooperate with Thadius’s plan. While one may originally think Thadius was referring to the big lid on the top of a piano, it is actually completely possible that Thadius was referring to the keylid instead, aka Oscar’s mouth. Keylids on grand pianos have built in locks, which the lids on top don’t have. In addition, this would also make the phrase “lock your lid and throw away the key” a dark variant of locking your mouth and throwing the key away, which would be fitting considering the fact that Thadius would later name his dungeon, where he tortures instruments, the “Orchestra Pit”.
Lucius and Tank started living in the palace when Thadius was still a little kid. This means that in the best case scenario, Lucius was completely apathetic to Thadius’ abuse of Oscar like Thadweena was. However, given that Lucius tends to do things to try and advance his own selfish goals with very little if any regard for others, he very likely joined in on Thadius’ abuse of Oscar to give Thadius a good opinion of Lucius.
When Thadius banned music from the world, not only did he take away a source of entertainment and hope, he also ruined so many people’s lives in doing so. Think about how many people lost their jobs, how many businesses were shut down, and how the people who didn’t comply were brutally “taken care” of when Thadius banned music from the world.
Not only that, but every musical instrument in the world suddenly found themselves being discriminated against overnight, and many people probably flat out abandoned their instruments once music was made illegal and simply being an instrument would make you a target.
In "Black Keys", the music museum that Oscar and the orchestra enter in search of another piano is an absolute mess. There’s papers on the floor, a broken chair laying sideways on the ground, and a glass tank that looks like it’s been blown up from the inside. Something terrible must have happened in that museum for it to have ended up like this, as the walls and ceilings are in too good of condition for it to just be falling apart with no one to look after it. Thadius probably had the things in the museum blown up and destroyed after he came to power.
In that museum, the orchestra finds Sammy, a turquoise-colored child piano. He tells the orchestra he used to belong to the museum keeper’s little boy. Considering Sammy is living at the museum by himself, either he was abandoned by said owner and his family, or Thadius had said owner and family killed.
Sammy has been living in that ruined museum all by himself, probably since whatever terrible event happened there, and judging from his exclamation that “(he) thought Thadius got everybody!” he’s almost certainly seen or heard something nightmare inducing. No wonder he’s scared of the orchestra at first.
Chordelia, her grandfather Claude, and Sammy all are implied to go back to the place where Chordelia and her grandfather were hiding previously at the end of “Black Keys”. But not only do the villains know where said place is now, as they found and captured Chordelia and her grandfather earlier in the episode, but Chordelia still has a tracker chip in her case. The villains can hunt her down and find her whenever they want, and Sammy and her grandfather are likely to get caught as well if Lucius or Thadius want revenge, which knowing Lucius and Thadius, they probably do.
In the first episode, we see a cello playing music for money on the street. We never see that cello show up ever again. It's completely possible Thadius caught him.
