Actor Shipping: Inverted. Many fans shipped Walter Girl Paige with Rabbit when Paige Law and Bunny Bennett were dating in real life. This also applied to Walter Girl Brianna and The Spine when Brianna Clawson and David Bennett were still together.
This has already started happening with The Spine and Rivet (an original robot character created by David's girlfriend Gabi) as well.
Alternate Character Interpretation: Some fans see Peter Walter I as a Mad Scientist who treated Delilah like a prize to be won without regards to her feelings, and see him as taking advantage of his maid Iris Tonia's infatuation with him to get her in bed. Interpreting any of the bots as a Stepford Smiler is also becoming increasingly popular in fanworks.
Which would make the song "Brass Goggles" a rare moment of honesty. "Photographic Memories", too, as the entire song is The Spine's mourning.
Base Breaker: Holy mother of god, Rabbit's Gender Swap. When it was announced via Bunny's blogspot, the fandom reaction ranged from overjoyed that the band would get another female and supportive of Bunny being able to fully identify with Rabbit, to enraged that such a massive change would be taking place, to worried that an openly transgender character would impede the band's future success. Some fans have even accused Bunny of being selfish for making the change, and have vowed to leave the fandom because of it.
Bunny later caused a bit of a stir among people who are still fans of Jon, when she revealed that she personally thinks Jon's contributions to the band's second album were probably the weakest songs (or, at the very least, that the songs just didn't fit in well with the other music on the album). It's worth noting that she says she still enjoys "Juju Magic," but only the live version, as she feels the album version messed up the song's quality. She later replied to at least one fan about the comments saying that people really need to calm down and remember that, unlike most fans, Bunny actually knows Jon on a personal level, and feels it's not unprofessional of her to critique the music of a former band mate.
As if Bunny declaring Rabbit's Gender Swap was enough to split the fandom into pieces; her Dark Humor referencing anorexia and self harm after Midwest Media Expo nearly caused a nuclear meltdown. Tumblr reacted in the extreme with threats of all sorts being thrown about by all sides of the debate. The ensuing chaos caused Bunny to go into what many fans at the time speculate was a full-on mental breakdown and delete her Tumblr entirely after posting what appeared to be the entirety of her inbox filled with anonymous messages containing everything from reassurance from those on her side, to death threats from those who were upset by her humor. She has since apologized for her comments at the time, but there is still debate raging as to whether or not she was indeed in the wrong for what she said.
David (who, like the rest of the band, is an Atheist) made several mildly disparaging comments about religion and religious beliefs on his Tumblr in early 2015. The reaction was as expected.
Epic Riff: The guitar in "Automatonic Electronic Harmonic" and the keyboards in "Ju Ju Magic".
Fanfic Fuel: Several parts of the band's history have yet to be elaborated upon, or left deliberately ambiguous, such as the stories behind some of the albumartwork, the backstories and fates of song characters such as The Suspender Man and Airheart, The Spine's desire to be human, how the Walter Girls came to work for Walter Robotics, and why Rabbit and the Spine have green eyes despite being powered by Blue Matter.
Bunny herself encourages this during her art livestreams, revealing huge chunks of information about certain aspects of the band's backstory while keeping deliberately vague (or silent) about others. She once teased, "There's a lot of secrets in the Walter family—and we're just scratching the surface."
Harsher in Hindsight: The band's jokes about how the audience should "enjoy [the Jon] while he lasts" because of his finite fuel supply became this when he actually left the band.
Ho Yay: Hatchworth's debut at the Youmacon concert was filled with a lot of him being very close with The Spine.
The Spine: Hatchworth, tell me again how much you love me. Hatchworth: Oh, very much.
Hatchworth:(in response to a fan's compliment) Oh, thank you. You're my favorite pretty girl in a pretty dress. (to The Spine) That is of course except for you, The Spine.
Another moment happened when Hatchworth is stuck on one knee with a hand raised to the Spine, Hatchmeister asks Rabbit to fetch a ring out of his back pocket to which the Spine smacks Hatch's hand away saying:
Love It or Hate It: The band is either made up of excellent performers who utilize their Steampunk aesthetic to show off the full range of their talents, or average musicians who simply hopped on the steampunk bandwagon to get popular.
Misaimed Fandom: As evidenced by one couple who considered using it as their wedding song, there are at least a few folks who see "Honeybee" as a straightforward love song.
The same applied when Walter Girl Carolina replaced Brianna. Even when the news broke that she would be replacing her permanently, the steady stream of love and fanart for her never slowed.
When Hatchworth himself left and Zero took his place, it was averted once more. The fanbase was sad to see the former go, but response to Zero was just as positive.
The Scrappy: While not as extreme as other examples, quite a few fans dislike Upgrade, seeing her as a useless addition to the band with sub-par vocals and an annoying personality. To a far lesser extent, the Jon has been seen as this since he was fired, with some saying he was holding the band back from achieving their full potential and contributed little creatively.
Tearjerker: Most of their songs are pretty lighthearted, if not comedic, but some are ... less so.
Especially if you believe the popular Fanon that the song was inspired by the death of Walter family member P.A. Walter IV, a NASA astronaut who was killed in an unexplained explosion about his ship.
Word of Bunny, compiled here along with other Vice Quadrant plot points, confirms this as canon. Except he didn't die. As per the Vice Quadrant timeline linked on the main page, he survived the explosion (which his involvement in has only been documented for Universe Omega, as he had already become Commander Cosmo in Universe Prime) and would meet Cosmica two years later.
The malfunction that occurred during the February 17, 2013 show. The 'bots had a sudden breakdown between sets, and booted up with a little-used file ... containing the events of the 1897 Copper Elephant War. The result was nothing short of heartbreaking.
Rabbit: (frightened) Pappy! Pappyyyyyy!
The Spine: Rabbit! Rabbit, you must get up...
"Turn Back the Clock" has become infamous within the fandom for the amount of tears it has caused.
Where'd my girl run to? Will she be back soon?
Quintessential isn't short of these either, particularly "Photographic Memories"
All those memories I can't wash them away they are embedded in my brain and I am all alone now
The Woobie: The fan's reactions to Hatchworth's debut performance was mostly a chorus of "awww"s.
Averted when he seems to become aware of the effect he has on the audience.
"I just wanted to bait the audience and get that 'awww.'"
What Do You Mean, It's for Kids?: They maintain that they're fairly family friendly, which is mostly true... But then you get into songs with existential angst (Brass Goggles, Wired Wrong), suicidal narrators (Honeybee, I'll Rust with You), and even an occasional Family-Unfriendly Death (Fire Fire). Though most of this is in somewhat coded references that a young listener wouldn't hear.