About the characters

- First mention of the last name of a doctor at the hospital.
- First time Yumi almost falls into the Digital Sea.
- First time Odd is admitted to hospital.
- Third time Ulrich is frozen by a Blok.
- Fourth season 1 episode in which Jim is absent.
- Odd went into cardiac arrest; he was saved before total death by the return to the past.
- Ulrich isn’t very good at physics, but Odd is.
- Jeremy dreams about Aelita and says that XANA can’t attack humans directly.
- The principal says he cannot let students leave Kadic, being under his responsibility.
- XANA’s song is called “Glad When You’re Bad” and the one Odd listens to at the end is “Under my Coat”.

About errors

- In a number of shots, the activated tower’s halo disappears.
- During Ms Hertz’ class, the students are from mixed classes.
- Herb’s collar is green instead of white and his hair is entirely black.
- Ulrich’s pencil disappears from his desk when he leaves his room.
- The door to Odd and Ulrich’s room changes often changes colour (grey, brown and red).
- At the moment when Sissi leaves the science building, her headband is black instead of yellow.
- The mouse and mouse pad for Jeremy’s computer disappear when he says to Ulrich “whatever you say”.
- When Ulrich leaves his room to sleep in Jeremy’s, the door handle is on the left instead of the right.
- At the moment when the RTTP is launched, we see that it’s night time though the episode took place during the day.
- During the RTTP, Odd no longer wears his silly grin and his eyes are closed, and the curtains of his room are closed.
- At the moment when he is virtualised, Ulrich’s sabre sheath is on the right instead of the left, as well as when he is frozen by the Bloks and three shots afterwards.
- When Yumi takes her skateboard, Jeremy’s scooter is absent even though Jeremy is at the hospital with Ulrich.
- Three Kadic students and Ms Hertz are standing in the hospital when Jeremy goes to talk to Aelita on his laptop, and again when the music takes effect on the whole town. Mr Delmas stated earlier that he can’t allow students to go off the grounds during the day, so they shouldn’t have been there.
- After Aelita enters the tower and the code, her outfit is reversed, her bandages and earring on the wrong side.
- Jeremy’s pants are blue instead of khaki and Ulrich’s pants are brown instead of green and his shoes black when Sissi, Herb and Nicolas walk past their table.

About the series

- French title: Musique mortelle
- French title of Glad When You’re Bad: Vous ne devriez pas

- During the school day, students can’t leave the grounds.
- First episode in which Ulrich and Jeremy go to the factory together, just the two of them.
- First appearance of Yumi in the Mountains.
- First mention of the hospital.
- First mention of RU Flicknight!
- First mention of the co-ordinates of the return to the past, and the first time we see Jeremy enter them.
- First mention of the music Odd has downloaded called Glad When You’re Bad and Under my Cover!
- First time wind is visible on Earth, at the entrance to Kadic’s park!
- Only episode written by Sophie Dubreuil.
- Only season 1 episode in which we see Ulrich leave the scanner, and spend the night in Jeremy’s room.
- Reappearance of the news presenters and reporters.
- The radio channel Yolanda listens to is the same as Sissi’s.
- In the deactivated tower in the Forest, Aelita sits in exactly the same pose as in episode 11, “Plagued”.