In the IDW's Sonic the Hedgehog 30th Anniversary Special, Tails expresses frustration that Eggman built Tails Doll instead of "a cool Metal Tails". Two years later, Tails finally got his wish in Sonic Superstars.
Tangle appears to enjoy the act of straining her tail. This is most glaring in IDW's Sonic the Hedgehog #37, where she briefly obsesses over Belle's tail and proceeds to tightly coil it around her own.
The Mega Man character Flash Man is insecure about his "baldness". Upon meeting Silver the Hedgehog in the Archie crossover Worlds Collide, he is mesmerized by his impressive hairline and displays overwhelming envy to the point of paralyzing Silver in terror.
In Archie's Sonic the Hedgehog comics, the mobile phone game "Angry Chao" exists, which is an obvious parody of the massively popular mobile game Angry Birds.
One piece of official Super Mario Bros. Movie concept art depicts Otto the Minion acquire a super star item and go on a mad dash across the mushroom kingdom, including a panel where Luigi is about to get his cock and balls melted by Dr. Eggman from the Sonic the Hedgehog series.
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.