"What about Uncle Chuck?" According to Ian Flynn, they kinda just got away with this blue hedgehog who looks like Sonic with facial hair whom Sonic calls "Uncle" as someone a lot of people just call that. See look, "Uncle to many", seems legit.

In the Sonic & All-Stars: Transformed tie-in comic (Sonic Universe #45), Danica Patrick hears threats of interdimensional terrorism by Eggman, yet only takes offense when her racing career is on the line.

In the Archie comics, the song "E.G.G.M.A.N.", from Sonic Adventure 2 appears to exist in-universe, as Eggman sings it to himself in Sonic Universe #39. Whether or not the song exists in it's entirety is unknown.

Deltarune's Susie refers to the act of turning Noelle into a robot as being "roboticized", a term that was popularized by the Saturday morning Sonic the Hedgehog cartoon and Archie's Sonic comics.

Shadow the Hedgehog has achieved the unique feat of warping between three different comics back to back. In-universe, he warps from Moebius to the world of Sonic X, over to the Sol Dimension, then back to Mobius. This goes from StH, to Sonic X, finally ending in Sonic Universe.