Vitriolic Best Buds: Sonic, Tails, Eggman, and Jim by season 5. At this point, they can't even bear to not hang out with eachother.
The main character of the show who is always looking for a job but fails almost all of the time. He is really lazy and rude but there are several moments where he does feel like he's accomplished something.
Abusive Parents: He wanted to kill Soniqua off until he found out that she helps him out in threatening situations.
He also wanted to wipe his and Lucca's children out of existence.
Broke Episode: Inverted, most of the series is about Sonic being broke. In Season 3, he becomes rich off of mafia money, before losing it all.
He does become rich in Season 6 due to time traveling though.
Brilliant, but Lazy: A number of times, such as in Tapper,Burger Time,Atari, and Star Craft Sonic is shown to be actually competent at his job. However, his short attention span and low tolerance for other people mars things.
Desperately Looking for a Purpose in Life: By Season 7, Sonic has been a mafia boss, a movie star, went to space, travelled through time, became rich, died, came back to life and done everything he has ever wanted be be. Thus, he drags everybody along to find the Creator, so he can know that there's still some greater purpose for him.
Idiot Hero: While others (Usually Tails or Eggman) are on occasion to blame, nearly all of his failed jobs stem from his inability to stay on task or care. He also drinks lead on occasion for no reason.
Not so Above It All: Tails feels like he's the only competent person in the group in season 3. However, during his short tenure as Mob boss, he is almost as bad at his job as Sonic.
Only Sane Man: Most particularly in season 3. His competence since then has dipped slightly.
Power Floats: But it's really impractical, since Tails can already fly. Lampshaded as well.
Long time enemy, new time friend of Sonic. After being little more than a nuisance in Season 1, Eggman comes to realize that he has nothing to do with his life if Sonic dies, and eventually becomes his friend.
Adipose Rex: In Season 6,he steals Sonic's time machine to fix his past mistakes. The end result is that he does win, but he also invents the incredibly-fattening Taco Sandwich and becomes an immobile blob.
Big Bad: He was a recurring villain and nuisance in Season 1.
Ditzy Genius: His robot building skills mostly see use in building deep fryers and funny-looking but useless upgrades for machines. However, as seen in "Falco," he can create actual weapons if he's not distracted. (He still couldn't hold off the deep fryers though)
Jim: <Drinking from a water bottle> "Why do I hang out with you assholes?"
Sonic: "Don't drink that; it's a roofie cocktail I made for the cheerleaders.
Unlike the friendly Kirby, this incarnation of Kirby is a psychopath. He murders innocent creatures and is known to randomly eat anything. In Season 4, he becomes a famous movie director and tries to help Sonic out.
Yes-Man: In Season 4, he loves everything Sonic and Tails say, but sometimes immediately goes back on that.
Sonic's and Mother Brain's daughter that was born after Sonic (He was drunk) had sex with Mother Brain. Mother Brain quickly gave birth to her, much to Sonic's chagrin. Sonic initially wanted to kill her off, saying that it'll prevent him from paying child support. However, after Soniqua saves Sonic from getting killed by Goro, Sonic values Soniqua (a lot more than Tails, that's for sure).
Parental Neglect: Niether parent is really sure what gender she is. Sonic starts off as an Abusive Parent, but even after he improves, she still goes off to battle Pokemon by herself and spend time in hell.
A very incompetent and unpredictable ally, Thunderhead can get on anybody's nerves. Sonic meets him and he orders Sonic to have sex with Tyris, which Sonic finds disgusting. Even though this backfires, Tyris seems to like Sonic enough to help him against Mario's Mafia. He had a temporary stay at Sonic's mafia office, but once the crew started drifting away, Thunderhead got sent to jail after starting a bar and committing some crimes, and has gotten an obsession with "ass-wine" (putting a condom full of wine up his ass).
Future Loser: Retroactive version. His modern day loser burger-joint-owning self appeared first, followed by his hopeful and relatively joyful self. When Sonic and company attempt to fix the timeline in season 6, Knuckles expressed distaste at his current status in life and tries to save himself.
Easily Forgiven: After Sonic tries to kill Mother Brain, she forgives him after being shown "cable satellite television."
Un Entendre: Although she makes a lot of innuendos, on at least one occasion she did it by accident.
MB: "I told [Frank} that there's always room for a giant worm in my cockpit, but it was going to cost him!"
Dominique Wilkins Poster/Person/Creator:
A former NBA Basketball player who played for the Atlanta Hawks, he is heavily featured on the poster that Sonic really likes to watch. After the poster's death in Season 2, Sonic orders Dominique Wilkins to be frozen in carbonite.
God: In a VERY big twist, he turns out to be this at the very last episode.
A commonly recurring character in Mega Man Dies At The End, Dr. Wily was a former mad scientist. He has connections with Eggman and Mario, as he went to Podiatrist School with Eggman and joined Mario's mafia to kill Sonic. However, there doesn't seem to be any callbacks referring to that. He (in another timeline) gets killed in Season 6 by Soniqua.
Plot Hole: Wily's presence in Mario's mafia isn't really explained, although the two sprites used are different (Mafia Mario's Wily is 8-bit while MMDaTe's Wily is tanner and 16-bit)
Once a princess saving plumber, now a high-end Mob boss. After Tails borrows money from Mario to bail Sonic out of jail, Sonic has to play hitman for the mob. After Sonic accidentally fails a mission and then lets Luigi get ran over on the following mission, Mario sets out to kill Sonic. Mario sends his Mafia friends to kill Sonic, but Sonic's friends help Sonic out and Sonic kills Mario, taking over the mafia. In Season 6, Princess Potato goes back in time and revives Mario, who wants revenge on the hedgehog.
Arson, Murder, and Jaywalking: Kills Sonic for destroying Mario's business, letting Luigi get hit by a bus, and programming Mario's DVR so it records each episode of Bachelor Pad like three different times.
"I was about to get a movie dear with Brett Ratner. BRETT RATNER!
Seppuku: Commits this once he finds out Sonic betrayed him.
A minor villain in the series, El Padrino is Red Falcon with the personality of a cocaine addicted South American druglord. He has his minions along with a bunch of coke whores who work for him. In Season 3, Tails serving as the mafia leader temporarily sends Eggman and Earthworm Jim to get a bunch of cash and cocaine from El Padrino. However, it seriously backfires as El Padrino decides to keep the two for entertainment and the two love the cocaine so much they decide to stay there. In Season 4, Sonic takes the two back, but El Padrino sends the "Marmosets", the coke whores on him, but Sonic easily takes them out and El Padrino lets them go.