According to Ian Flynn in the 9/16/19 BumbleKast, Sally and Nicole were intended to have a romantic relationship post-SGW. This wasn't met with the book being canceled, but it would have made them the first (if not, one of the first) bisexual Sonic the Hedgehog characters.
In Archie's Sonic the Hedgehog comics, Knuckles died, entered the afterlife, and was sent to be resurrected 3 issues later.
The third issue of the Sonic Forces prequel comic features a cameo of Sally Acorn. This is notable, because this was after Archie's Sonic the Hedgehog comics were cancelled.
Adventures of Sonic the Hedgehog storyboard artist Milton Knight describes this show's version of Dr. Robotnik as "the perfect image of self love", even calling him "animation's sexiest fat man". "He believes in his own romantic self and his own sexiness."
Super Mario-kun is a manga series that has adapted various games in the Super Mario series starting with Super Mario World. To celebrate the release of Mario & Sonic at the Olympic Games Tokyo 2020, Sonic the Hedgehog and his friends appeared in a one-shot.
Amy Rose seems to be the only character in the main Sonic the Hedgehog cast who can handle a casual punch from Knuckles.
Scott Pilgrim's high school band "Sonic & Knuckles" is a very subtle reference to the 1994 Sega Genesis game Sonic & Knuckles.
Sonic the Hedgehog does not know what hedgehogs look like.
Whisper the Wolf's design began with an in-game custom character in Sonic Forces. From there, she would gradually evolve into her final look.
Tails is very discontent with the fact that Eggman has settled on making Tails Doll rather than a Metal Tails. Moreover, this suggests that he finds Metal Sonic and Knuckles to be particularly cool.
When robots or lackeys fail, Eggman uses his built-in command grab
In 2015, it was revealed that Ian Flynn, Tracey Yardley!, and Ben Bates of Archie Sonic the Hedgehog fame had pitched a line of Super Mario comics to Nintendo. It was ultimately rejected. Allegedly, Mario was also intended to cross over with Sonic and Mega Man in comic form.
Knuckles the Echidna's father dies of pancreatic cancer in the Archie Comics.