About the characters

- Jim claims to have been a salvage diver in the Marine Corps and no longer accepts Jeremy’s excuses to stay away from the pool.
- Odd says nightmares happen all the time and he had a crush on a girl from a chatroom before realising that it was actually Sissi.

About errors

- When Aelita is led through the corridor by Jim, both male and female students poke their heads out of the doors to see what’s going on. We see Jeremy’s room, so we can assume she was on the boy’s floor, so there shouldn’t have been any girls in the bedrooms. We then see all the lights switched off on the girl’s floor.
- Aelita’s outfit is reversed just before she enters the Code Lyoko.
- Just before Aelita falls into the pool, Jeremy’s board shorts change colour and two students change place.
- Jeremy’s tray is empty at the moment when Odd gets ready to leave the cafeteria then it becomes full again in the following shot.
- Aelita’s earring disappears when she says she’ll only take a few more seconds with the interface in Sector 5.
- The factory microphone is in Jeremy’s right ear when he says “Virtualisation” for Aelita and Yumi, and it changes constantly (wired or wireless).

About the series

- French title: Empreintes

- Only episode in which the Scyphozoa attacks Aelita twice.
- Third episode beginning with one of Aelita’s dreams.
- Sissi (to Aelita): “Was that you screaming, huh?”
Sissi makes an allusion to episode 31 “Mister Puck” in which she became fed up with Aelita waking her in the middle of the night after screaming because of her visions.
- Allusion to episode 28 “Unchartered Territory” when XANA sends the Transporter for Aelita to use and send her to Sector 5 alone.

About references

- Odd: “Hey Cinderella, we said midnight on the dot!”
He references Walt Disney’s famous animated film in which Cinderella is transformed by her fairy godmother into a beautiful princess, but the spell only lasts until midnight. The film is based on the story by Charles Perrault.

- Jérémie: “It’s a poem by the guy who wrote The Little Prince!”
Antoine de Saint-Exupéry is a famous author.

- The English title of the episode comes from the film “Déjà Vu” by Tony Scott. Déjà vu is also a medical term coming from French (literally meaning “already seen”) in which the person experiencing it feels as if they’ve done an action or been to a place before, when they actually haven’t.

- Jim: “Don’t forget Archimedes’ principle: any body plunged into a liquid and…um…”
Archimedes of Syracuse was a Greek scientist, mathematician and engineer from Sicily. The correct phrase is, “Any body wholly or partially immersed in a fluid experiences an upthrust equal to, but opposite in sense to, the weight of the fluid displaced.”