Acting for Two: Anyone who has a second character, excluding Omega Zell's attempt at Cross Playing and Saphir's Gaea look-alike avatar (don't ask), that is more of case of acting for three for the actress playing Gaea.
Actor Allusion: Generally speaking, anyone who was in one of Fabien Fournier's previous creations (e.g. around half the cast) had something carry on from their previous characters. The elements from Lost Levels tend to be the most obvious due to Noob being its Spiritual Successor.
Jibédix and Rubis are played by the Reflets d'Acide creator and his girlfriend. In French "Jibédix" sounds just like "JB-10" and Rubis's background is managing a guild named Trichelieu on a game called "RDA online".
Actor-Shared Background: All the cast had to spend at least some time in the south of France (where all Noob guild players live) to know the series creator in the first place and quite a few of them are actual gamers.
Cast as a Mask: An inversion of the trope can occur when whatching Lost Levels after watching Noob. Heimdäl's mask is an allusion to a character his actor was playing in that series, and that character was actually wearing a mask in-game to conceal his identity as someone already seen in real-life parts of the story. If you recognize the actor of even his name in the credits the first time he appears, the identity of the masked man that appears later is obvious.
The actor playing Sparadrap is one of the non-gamers of the cast, making him geunineley ignorant of the subject.
Meuhmeuh is an accidental case. The actor has trouble keeping balance in the shoes he wears for the costume, but the character is somewhat of a Keet. The result is that only about half of the onscreen clumsiness is faked.
Older Than They Think: The audience first assumed that the series was inspired from .hack. It was actually based on an older web series by Fabien Fournier, Lost Levels. However, an homage was done to this legend in Season 2 premiere : the first appearance of Kevin (the player behind Sparadrap) is in a wheelchair, (and with a Stephen Hawking voice) just like Subaru. It turns out that Kevin was just playing with his grandma's chair.
In addition to Lost Levels, Noob shares elements of an audio spoof of World of Warcraft. Some characters existed as early as that spoof, but the noob was the tank, named Fungliboss. Most Noob characters are however meant to be an Expy of their Lost Levels version.
Syrial, a movie made around the same time as later episodes of Lost Levels, had early apperances quite a few elements used in the novel, especially the second one. Some of the characters ended up in the webseries, such as Pironess and Tabris. The general idea of Centralis first appeared in that movie also.
The Pete Best: In Season 2's two last episodes, team Amaras' female nuker had a different style, was played by another actor, and was never named. The Roxana described in the character sheet was only set in stone in the second novel, which takes place between Seasons 2 and 3.
Real-Life Relative: In general, the cast is a group of Fabien Fournier's friends who bought in their own acquaitances, who themselves knew other people. When cut down to couples and siblings, you still have :
Johanna Fournier (Ivy) and "Gabrielle Jolivet"/Anne-Laure Jarnet (Gaea) are respectively Fabien Forunier's (Fantöm) sister and wife (as of July 2013). Matthieu Zecchini (Ystos) is Fabien Fournier's brother also.
Lionel Tagliavini (Master Zen) is Amandine Tagliavini's (Golgotha) brother and Frédéric Zolfanelli (Sparadrap) is her husband. Golgotha's mage actually existed because of Amandine Tagliavini's pregnancy, so she would have a more adapted costume.
Julien Guellerin (Omega Zell) and Amandine Train (Saphir) are together and seem tohave at least two children.
"Gabrielle Jolivet"'s grandfather played One-Scene Wonder "Papy PK" (Grandpa PK).
Serwan Melk (Meuhmeuh) and Carmen N'Guyen (Pironess) are a couple as well.
Talking to Himself: A meta-case happens in the third novel, where Gaea and Saly Asigar briefly exchange a few words. One of the planned Noob spin-offs will have Saly Asigar played by Gaea's actress.
The partial overlap between the media usually takes care of this trope, but Heimdäl and Arhtéon's intended past as best friends escaped that safety net. The two have only interacted twice so far in all three media taken together, and always in circumstances where any random player who did the same thing as Arthéon would have gotten similar response/support from Heimdäl. The only remanents are Arthéon's mentionned past as a Justice guild strategist and their shared practice of roleplay that is blurred out by the fact that the whole Justice guild main roster is made of roleplaying fans.
Acocrding to the Season 5 making-of, the hidden father-son connexion between two certain characters was a husband-wife relationship in the early drafts of the story.