Junior repeatedly refers to Yang as "blondie". Barbara Dunkelman's screen name within the Rooster Teeth community (as well as her Twitter handle, Xbox Gamertag, etc) is BlawnDee.
Ozpin's hair colour is a shout out to Monty. Monty was originally going to voice the character until he decided his voice wasn't right for the part.
This is not the first time Jen Brown has voiced a proficient warrior with green eyes and red hair in a ponytail (Pyrrha Nikos)
Ryan Haywood still has a habit of locking up animals as Peter Port.
Burnie and Joel return as two quirky cops like in the Pirating short.
The full version of "Red Like Roses Part II" turns out to be a duet between singer Casey Lee Williams and her mother Sandy Lee Casey. This leads to quite a bit of Reality Subtext in the song itself.
In volume 2 Yang makes an Incredibly Lame Pun, something her voice actress Barbara Dunkelman is infamous for. This could technically count as Ascended Fanon as fans already had her making Incredibly Lame Puns in fanfiction and fancomics as soon as Barbara was announced as her voice actor.
In episode 4 of volume 2, it's implied that Yang has been doing it for a while now.
In volume 2, Roman refers to himself as a professional. Another antagonistic character also voiced by Gray Haddock, Locus from Red vs. Blue, has also done so.
Ren dancing should surprise no one, considering his voice actor.
Fandom Nod: In the fourth episode of volume 2, Team RWBY turns out to have codenames for particular attacks; specifically, when two members of the team attack together. The names Ruby calls out for some of these are Fan Nicknames - hilariously, some of them are shipping names (such as "Bumblebee" for Yang and Blake and "Ladybug" for Blake and Ruby).
Fan Nickname: Most of which are supplied by the wiki as placeholder names.
The fans used to refer to characters by their colors before their names were revealed. For example, Blake was Black and Weiss was, well, White. This carries on in a slightly different way later in the series, with the fandom using name colors from other languages as well.
Fans have been calling Junior's weapon the "Batzooka", saying he must have stolen it from Batman.
In the same video, we have DJ Deadb3ar.
Jaune will forever be referred to as Vomit Boy to some.
Before their names were revealed, Pyrrha was Umber, Nora was Apricot, and Ren was Nero. The first letters of their names, along with Jaune's, were meant to spell JAUN in the same way that Ruby, Weiss, Blake and Yang spelled RWBY. After their full names were revealed, ANVL became a short-lived placeholder, derived from their surnames: Arc, Nikos, Valkyrie and Lie (though Ren's surname is debatable). It was quickly replaced with JNPR (Jaune, Nora, Pyrrha, Ren) once Monty tweeted that it wasn't ANVL.
Continuing with weapons, Pyrrha's was called the Magnospear (derived from the word magnetosphere) and Xiflelin (portmanteau of xiphos, rifle, and javelin), Jaune's Sword and Shielth, Ren's Jade Dragons, and Nora's was Amethyst Thunder. Due to speculation of the importance of Jaune's weapon, it was often also referred to as Excalibur.
Roman Torchwick's weapon is often called Candy Cane.
Sun's bo staff/nunchucks/shotguns are referred to as Gunchaku.
Some of the techniques also get nicknames, such as Weiss's Air Step and Adam's OHK against the Spider Droid being called Seeing Red or Moonslice, the latter of which is based on a tweet from Monty with notes about what seems to be the Black Trailer.
Speaking of the Spider Droid, it and the Knight are still technically unofficial names.
The creature from the class in episode 9 captured by Professor Port was being called Edgar after a cow captured by Port's voice actor Ryan Haywood in Roosterteeth's Minecraft streams.
The two members of Team CRDL seen during the Initiation (Russel and Cardin) were referred to as Mohawk Guy and Armor Guy respectively.
Cinder is the witch that aids Roman in the first episode; fans like calling her Wicked Witch or Crimson.
The droids in the Black trailer are AK-130s. Due to the similarity in name to the AC-130 gunships - which are called "Spookies" - these droids are called such as well.
The Grimm creatures' names: Beobears (Ursa), Basilisks (King Taijitu), and Scorpius/Scorpi (Death Stalker).
Cardin's mace weapon is called Almace, or by others DoucheWhisk.
Team POGO: Professor Port; Ozpin; Glynda Goodwitch; and Professor Oobleck
Team QROW: Speculating the team up of Qrow, "Summer Rose", Ozpin, and Glynda Goodwitch... an alternative choice would be Roman in place of Rose.
Team Sloth seems to be a popular one on Deviantart and Tumblr.
Team Double-Date Night for JNPR due to how smoothly the two pairs ship.
Mercury's shotgun-greaves have gained the nickname Shoot-Boots in some circles of the fandom. Others have taken to calling them Talaria, after the sandals that the Roman God Mercury was said to wear.
Penny is suggested as being the daughter of Gepeddo.
Japanese fans have taken to calling Yang "Yang-nee" (Big Sis Yang) affectionately.
The grouping of Cinder, Roman, Emerald, and Mercury has acquired a number of unofficial Team acronyms: CREM (cream or creme), CRME (crime or chrome), MERC (mercenary or mercury).
With the recent apparent addition of Neo to the "team" as well as the reveal of Emerald's surname (Sustrai), a new acronym vastly more appropriate to the team (or at least its leader) has emerged: CRMSN (crimson).
Speculation for Sun's team members included Antares (for Scarlet) and Rex (for Neptune).
Neptune's weapon is called the Trigundao.
Following a Tweet by Monty revealing the character name Taiyang Xiao Long (presumably Yang's father) and the revelation that Qrow was on a team with Summer as well as Yang's parents, the team names TRQS (turquoise) and QRTS (quartz) have become popular at the RWBY wiki.
Certain circles have recently begun calling the Transient Princess as well as Yang's missing mother: "Raven" (the two are strongly associated).
Flip Flop of God: Sun's name was listed as Sun Wukon in the episode 16 credits, but it was Sun Wukong in the credits of episode 15. Presumably the G-less spelling is a typo, as other posts by Monty have used the G.
Pretty much everyone predicted Episode 15's reveal of Blake as a Faunus and to a lesser extent Episode 16's clarification of her former membership in White Fang.
After the release of the promotional material for Volume 2, namely, the group silhouette for Velvet's Team, it was pretty much a given that her team would somehow be named "Coffee."
Penny being a robot.
Many people speculated that Ruby and Yang are half-sisters, sharing a father, but fewer speculated that it was Yang's biological mother that she has been searching for in the Yellow trailer, and that Summer Rose, Qrow, the sisters' father, and Yang's mother were on the same team.
The Other Darrin: Visual example. The Beowolves were first introduced in the Red trailer, which Monty had been working on by himself. Later, they were redesigned by some of the concept artists and character designers.
Professor Ozpin was originally supposed to be voiced by Monty Oum himself. Matt Hullum also auditioned for the part, but it has been confirmed that he'll be voicing another character. Monty is voicing Lie Ren, but Matt's role hasn't been confirmed yet.
Gavin Free was originally slated to voice Junior. Though he was replaced by fellow Achievement Hunter Jack Pattillo, it has been confirmed he will play someone else in the series. This is somewhat humorous when one realizes the scene was originally Barbara putting Gavin's balls in a death grip. His signature scream probably would've been included, too. Given that Barbara and Gavin are one of the Rooster Teeth fandom's One True Pairing, the squees may have overwhelmed Gavin's scream somehow.
Many scrapped ideas regarding character design were shown on the panels at RTX 2013:
Ruby's hair was originally going to be gray, because Monty wanted to evoke a kind of wolf-like appearance for her. He mentioned later that Ruby's current hairstyle still looks kinda 'wolfy'. Her cape was also originally going to have a muff-like thing around her neck, but animation issues restricted that.
Both Ozpin and Glynda were going to have more cape elements in their design, but they were scrapped for the same reason as Ruby's cape-muff.
Roman Torchwick's early designs had a striped scarf.
Team RWBY wasn't supposed to have hair colors that matched their theme colors, and everyone but Yang was a brunette. So, Yang was the only one who ended up keeping her original hair color.
By the original plans, Jaune was actually on the right track in the cave in Players and Pieces, because the relics were going to be inside assorted Grimm, including the Deathstalker stinger.
Nora was originally meant to have a sash that wrapped around her waist, and ended in two long tails. Monty scrapped the idea because he thought it would be too hard to animate.
RWBY Volume 2: Production Diary 1 describes Velvet as simply having been created for the sole purpose for demonstrating the discrimination Faunus face, but fan response to her was so positive that she was further written into the story for Volume 2.
Kerry: It's a good thing we didn't go-we almost went with a dude with an elephant trunk. Probably wouldn't have turned out— Miles and Kerry: Not as good.
Early art for Ren implies that he was originally intended to be a more androgynous or even female character wielding a sword.
Similarly, early art for Blake gave her heterochromia and two differently colored cat ears.
Monty's earliest doodles of Yang, Pyrrha and Weiss and show some minor differences. Yang's pants and some highlights of her clothes were yellow and she had a different style belt. Pyrrha had some armor covering her sash instead of a belt, extra armor on one leg, and no tiara or ponytail. Weiss' clothes weren't as detailed, her jacket lacked it's red collar, is missing her black undershirt and had a different ponytail. Also, it shows a few early designs for her snowflake emblem.
Cinder at one point had incredibly long, flowing sleeves similar to Weiss.
Penny's curbstomp of the White Fang forces, where she clearly shows signs of being a robot (weapon popping out of her back, inhuman strength even by the standards of what had been shown, firing energy beams in a very mechanical fashion), was not intended to be in Episode 16, and was added by Monty Oum without prior knowledge. This is clear in the DVD commentary, where Miles Luna makes it clear he had intended Penny stopping the van to be the first indication of Penny's true power and identity.
During Mercury and Emerald's Establishing Character Moment of their assassination of Tukson, the crew considered adding an extra shot of some of Tukson's blood on a wall.
He seemed very fond of the Nora mafia princess theory.
Though many had assumed that the Faunus were inspired by the many animal characters that exist in anime, Monty Oum has revealed that they actually stem from his love of the old Hanna-Barbera cartoon Snagglepuss. (This is probably Trolling Creator).
His Twitter responses tend to be vastly more serious and definite when it comes to answering questions and debunking Fan Wank. Most notable so far, he has made it clear that Yang and Ruby are half-sisters that share a father and confirmed that Summer Rose is Ruby's mother, as well as having died before the series starting point.