I tried doing a Sonic fan comic several times in my life. My latest attempt was in 2004 and this pic sums it up.  
“Chaos Syndrome”‘s story picks up right after Sonic Adventure and features the characters of Chaotix.  
In my interpretation, the Chaotix gang disbanded after their adventure in the game “Knuckles’ Chaotix” and each member went their own way. Tails and Amy meet Espio who enlists their help to reunite the other members of Chaotix once again.  
I stopped this comic after the 3rd chapter (Charmy’s appearance) because I was too busy with MNT Gaiden…  
Even if it’s discontinued, Chaos Syndrome lives on in MNT Gaiden - as short as Chaos Syndrome is, it allowed me to experiment on the various themes and character developments. Those elements are vastly expanded upon in MNT Gaiden.  
Thus - MNT Gaiden is kind of the definitive version of what I had in mind for Chaos Syndrome. ^^;  
Anyways, for those who didn’t read the 3 existing chapters of Chaos Syndrome, here’s a rundown of the characters in it. Don’t be surprised if they remind of you if they remind of you my other projects:  
-Tails: The do-gooder, very naive and believes in everyone’s potential to be a good person. Due to his good nature, he’s usually the one who’s the most receptive and understand of everybody else’s problems. His naivety often gets on Espio’s nerves.  
-Amy: The tsundere of the group. She wields her PikoPiko Hammer to punish those who harass her, namely Mighty. Although sometimes shallow and simple-minded, she genuinely cares for Tails as a pal and won’t hesitate to stand up for him.  
-Espio: The serious, no-nonsense and hot-tempered temporary leader of the group. Whenever something goes wrong, he’s quick to blame Tails for just about any reason and usually hits the poor fox on the head (or strangles him when he’s really mad). However, deep inside, he cares for all his comrades, even Tails.  
-Mighty: The resident pervert and joker of the group. He is completely obsessed with Amy and does/says things that are borderline sexual harassment. He somehow survives all her hammer attacks thanks to his tough shell.  
-Vector: He took all the credit for saving Carnival Island and is now a popular DJ. He’s pretty much a corrupted bastard until he realizes the error of his ways and abandons his rich life to join his comrades. He’s an optimistic guy who acts like a big bro to everyone.  
-Charmy: Since I based him off anything but the Sonic Heroes game, he’s not childish and actually quite smart. He became a pharmacist and grows all kinds of exotic plants in his underground garden thanks to a Chaos Emerald until his own garden turned against him.  
-Sonic: He’s missing in action. Tails gets a glimpse of him absorbing a chaos emerald of its power, leaving it with only negative energy. His motivations are unknown to the others.  
-Knuckles: (did not yet appear in the comic) He’s the one who asked the Chaotix to reunite once again.  
-Tikal: (did not yet appear in the comic) She knows something about the chaos emeralds acting strangely, but will only share her knowledge with Sonic.
 
All official Sonic characters are (c) Sega.  
Song of inspiration: “Kyou egao ga areba” (Gatekeepers 21 opening)
 
NOTE: I believe this comic cannot be found anywhere online right now. If it’s somewhere, chances are it’s also in French. One day, I’ll scan it all and post it here. But it’s old material, so it won’t be very pretty. ^^;  
NOTE2: LadyJane6374 pointed out that the 3 chapters of Chaos Syndrome are still online in English at [link]  
Thanks, LadyJane6374!