Big the Cat is a himbo.

Sonic the Hedgehog has blue hair and pronouns (he/him).

In the Japanese manual for Knuckles Chaotix, Vector the Crocodile is revealed to be a Christian.

Gold the Tenrec Creator Evan Stanley stated on her Tumblr blog that she was leaning towards having Gold be either bisexual or lesbian during her time working at Archie. Unfortunately, the comic was canceled before this could be demonstrated in-universe. https://t.co/Yzmn3ooPGA

#AskSonicHey everyone, I have a question for Amy! Those rings look suspiciously similar to Shadow's inhibitors, are you holding back some sort of power?

According to Sonic lore, these are the same character.

Cream the Rabbit and Cheese the Chao's names are based on, well...cream cheese.

Sonic Rivals and newer material states that Eggman Nega is a descendant of Dr. Eggman. By the simple act of existing, this proves that Eggman either has sex or will inevitably have sex in the future, with a long lineage lasting for at least two hundred years.

Knuckles has a really long head.

While it's not outright stated, it's highly likely that the species chosen for Jet the Hawk, a professional user of Extreme Gear, was inspired by legendary skateboarder Tony Hawk.

Amy Rose's leg is clipping through her boot in her Shadow the Hedgehog render.

According to Ian Flynn in the 12/21/20 BumbleKast, his vision of a "Super Amy" consists of her having a pink/rose gold sort of fur coating, accompanied by her long hammer upgrade from Sonic Adventure.He has no logical explanation for the hammer, it would just look cool.