Adaptation Displacement: While the show hasn't eclipsed the Sonic games themselves, some fans are much more familiar with Scratch, Grounder, and Coconuts here to the point where there are those who believe that they were created exclusively for the show, even though they're actually all based off enemies from Sonic the Hedgehog 2.
Cult Classic: The show has a sizable fanbase. Most of its fans grew up with it.
Dancing Bear: Most people only care about "Boogey-Mania" for one line. One line that has nothing to do with its plot, no less.
Designated Hero: Sonic's attitude and mischievousness is amped a fair degree in this series, sometimes making his role as a hero pretty questionable. Though this is balanced out by his selflessness, his Big Brother Instinct towards Tails, and the fact that Robotnik is still trying to enslave Mobius.
Draco in Leather Pants: Robotnik. Many fans actually want him to beat Sonic despite still being as evil as his fellow counterparts. His Fountain of Memes and "the world's sexiest fat man" status certainly help.
The bounty hunters from "Sonic Search and Smash Squad", largely due to their reappearance in Dr. Robotnik's Mean Bean Machine, a rather extreme example of this since outside the game, most of the characters only appear for all of a couple of seconds in the show itself.
Evil Is Sexy: Catella, the co-antagonist of the episode "Zoobotnik."
Family-Unfriendly Aesop: The show has a couple of real winners when it comes to its attempt at giving kids helpful advice:
One segment advises kids against running away from home by having Coconuts try it, and Sonic remind him of all the good things Robotnik does to take care of him, and how no one will be there to do those things if he runs away, to convince him to go back home. The thing is, Coconuts is The Unfavourite among Robotnik's creations, and spends most of his time taking abuse and doing chores to clean up after the rest of the "family", so basically the message comes down to "Even if your family is abusive, it's better than risking it going alone".
In another, Sonic and Tails are surrounded by enemies, so Tails suggests calling 911. Sonic shoots down this idea, saying that 911 is for real emergencies. In other words, being attacked by people who wish to kill or seriously harm you is not an emergency. This was corrected in another episode.
Foe Yay: In the episode "Best Hedgehog", Sonic marries Robotnik as part of a prank and they're never technically shown getting a divorce. Sonic seals the deal with a big, sloppy kiss. In a later episode, "Sonic's Running", Sonic disguises himself as an attractive blonde woman and briefly seduces Robotnik to give his robot wife the impression the he was seeing another woman.
"Mass Transit Trouble", an episode about Robotnik attempting to bomb three separate transit stations, feels darker than the other episodes because of similar bombings in real life. It doesn't help that Robotnik and his henchmen are far more competent than usual.
In "Sonic Breakout", Robotnik imprisons Sketch Lampoon for making fun of him in a satire based on Humpty Dumpty. This is less funny to watch after the Charlie Hebdo attack in 2015.
One of the four part Chaos Emerald saga episodes, "Hedgehog of the Hound Table", has Sonic going back to medieval times. Guess what the second entry in the Storybook Series from the modern Sonic games is about?
Robotnik remarks in "Full Tilt Tails", "No wonder people say I look just like Santa Claus." In "Sonic Christmas Blast", he becomes Santa Claus.
In "Lovesick Sonic", when Tails is thrown underwater, a fish asks if Tails can swim. He tries using his dog paddle and says, "Not very well," before flying out of the waterfall. Then came Sonic 3 where Tails can actually use the dog paddle to swim, but only for a short time, as he will tire himself out if he swims too hard.
The way the sloths talk in "Slowwww Going". Fast forward to March 2016 with the Disney's Zootopia featuring sloths talking in a similar manner.
At one point, Robotnik kidnaps Sketch Lampoon, a comic artist, to make him create stories where he's the hero, and advises Sketch to make him look like a more muscular Top-Heavy Guy. Sonic Boom's incarnation of Eggman is a Top-Heavy Guy that looks less fat than any previous incarnations.
Supreme High Robotnik from "Prehistoric Sonic" is essentially a Super form for Robotnik in all but name and is defeated by Sonic taking the Chaos Emeralds away from him. Eggman would later return the favor in Sonic Unleashed by creating a machine to extract them from Super Sonic. What's even more hilarious is that to defeat Supreme High Robotnik Sonic needed to team up with himself from different points of time.
Coconuts, so very much. Especially in the Sonic Says segment of "Tails' New Home".
Scratch and Grounder are only marginally less pitiful than Coconuts, if anything their higher position leads to them suffering more abuse from both Sonic and Robotnik. Grounder's dopey, puppy eyed disposition doesn't help.
Robotnik himself comes dangerously close at times, especially in episodes involving his mother.
Moral Event Horizon: While Robotnik isn't anywhere near as terrifying as he is in Sonic SatAM, many of Robotnik's plans involve at best enslavement for life or at worst mass murder of civilians. For example, in "Sonic Gets Thrashed", his entire scheme revolves around killing his own robotic creations and enslaving many Mobian citizens. If that wasn't bad enough, in "Hero of the Year," even after capturing Sonic, he still plans on drowning everyone who attended the ceremony for Sonic, just For the Evulz.
Sonic could be seen as this as he sadistically tortures Robotnik, Scratch, Grounder, and Coconuts. Though it can be argued that they deserve it, and Sonic does it, as much for other bullied citizens, as for himself, they are so pathetic, people will feel bad for them regardless. When Coconuts decides to run away and possibly be good, Sonic tells him to stay with Robotnik, despite Robotnik's constant abuse. His scheme in the pilot episode also seemed reliant on Sonic being as obnoxious a customer as possible.
"Baby Sitter Jitters" introduces three baby beavers who give Sonic and Tails a lot of trouble in their one episode, which normally would be bad enough on its own, but then you see that the babies often intentionally harm Sonic, Tails, and later Robotnik and his minions, getting some sort of sick pleasure from it. And at the end of the episode, it's revealed that their parents left them with the hedgehog/fox duo just so they could have some peace and quiet, and since Sonic and Tails did such a good job, they get assigned another weekend with them. Add their annoying crying and ugly character designs into the mix, and you have yourself a recipe for three Sonic characters that literally no one could defend.
They Wasted a Perfectly Good Character: The show has some decent one shot characters. Perhaps most blatantly are Robotnik's earlier bots who, despite being utilized and even given names and personalities in Dr. Robotnik's Mean Bean Machine, make only cameos in the pilot and one or two more episodes if very lucky. The show also adapted Princess Sally for a voiceless cameo in the Christmas Special.
Robotnik himself in some episodes ("Lovesick Sonic", "Robotnik Jr."), where the expressive animation makes him look like a big orange teddy bear.
Vindicated by Cable: The show found grater popularity when it aired on Toon Disney following its launch in 1998, when Disney owned DiC at the time. The network's run was so popular that the channel aired the series for four years, every single day. This allowed people who were interested in the Sonic franchise to record almost every single episode for a new generation.
Vindicated by History: Thanks to the aforementioned Toon Disney run (and Pop UK's run as well), the show found new life during YouTube's infancy when a user named "sonicutie" uploaded most of the Adventures of Sonic the Hedgehog episodes, leading to their eventual use in various YouTube Poop, which kept the series from fading into obscurity.
WTH, Casting Agency?: Urkel for Sonic. A strange choice, to be sure, but what's even stranger is that it worked quite well, enough to do it on both Sonic shows that were running concurrently.
Usually Tails. Sonic also has his moments, such as the episode "Sloooowwww Going". It's even Lampshaded in this YouTube Poop. For all the Rooting for the Empire the show garners, it did like to offer hard reminders why they weren't supposed to lose.
Coconuts could be this when you realize he is actually trying to get a promotion instead of being evil.
Goopster the alien in "So Long Sucker" is quite The Woobie as well.