Amazing Technicolor Population: The Overlanders don't seem to have natural skin tones, instead having everything from pale green to pink to blue to stark white to gray and everything in between. That's not even getting into the blue/pink hedgehogs and otherwise technicolor Mobians.
Art Evolution: Inverted. The initial art style for the first story arc included shading and lots of details, but that became rather exhausting for the artist, so it regressed into a much simpler style.
Ascended Meme: On one update of the story "It All Started With a Hedgehog," the author accidentally placed Manic's nose such that it could be easily mistaken for Sonic's pupil. This led to a minor case of amused confusion in some of the readers, and the mistake has even spawned fanart.
Bad Future: Heavily implied for Silver and Blaze. Blaze specifically states that she was the only source of heat for miles, and the only thing Silver has ever “said” about his situation was a wordless image of him sitting alone in what appears to be a very large bookshelf.
Cast of Snowflakes: Every single character shown is easily distinguishable from one another.
On one hand, the fifteen main characters include two Jewish people, at least three noticeably dark skinned people, a chameleon from the Fantasy Counterpart Culture of the Middle East, two open homosexuals and their adopted children, two cyborgs, and a genetic experiment.
On the other hand, there are also two hedgehogs, a fox, an echidna, an example of Humans by Any Other Name, a crocodile, a chameleon, a bee, a rabbit, two robots, two half-robots of dubious biological species, a bat, and an alien who may or may not be imbued with hedgehog DNA.
The human portraits of the cast are also just as diverse; Sonic, Rosy, and Vector are Caucasian, Tails is South Asian, Knuckles is Jamaican, Espio is Arabic, Charmy and Rouge are African American, Cream is Japanese, Silver is albino, Blaze is Indian, and Shadow is Ambiguously Brown. There've also been hints that Eggman is Hispanic.
Floating Continent: There used to be about two thousand Floating Islands floating in the atmosphere, but ever since Surface War II, that number has been reduced to less than 200.
I Just Want to Be You: Metal Sonic REALLY wants to be “The Real Sonic”. So much so that he kidnaps Tails to learn the true meaning of Hanukkah, claims that having more stripes proves he’s the real Sonic, and dons a pink apron and tiny blue hat when he thinks about his situation a bit too hard.
Imaginary Friend: Vector and Cream share a power in which they can see every single Imaginary Friend ever dreamed up ever. The power can be turned off.
One Head Taller: Shadow the Stranger is considerably much taller than his Mobian acquaintances, best seen here◊ and here◊, though he’s actually just 4’7”, which isn’t tall at all by Overlander standards.
Science Fantasy: Whatever cannot be defined or explained by science fiction (such as the imaginary Nazo Immune Cell which grants Mobians and Overlanders their powers) is explained through more supernatural means (such as the Floating Islands all being kept in the air by hidden, ancient artifacts such as the Master Emerald).
Shown Their Work: In spades, particularly in regards to the world building. In brief, the moderator of the blog has clearly done her research on Judaism, World History, Spanish, Japanese, biology, astrology, and so on. There was even a modification made to Jet's character design when further research on Native American Culture unearthed some Unfortunate Implications.
Un-Sorcerer: Maria Robotnik. Being born without any Nazo Cells in her body not only meant she was born without powers, but also completely messed up her health, being unable to digest certain foods and having very, very weak muscles.
The Mafia: Possibly. Rosy tends to tiptoe around the subject of what her family does.