It's the long-awaited* return of the version of Sonic from Rikudou Koshi's "Sonic and Tails" doujin (with extra clothes) and her rambunctious past self who didn't exist in said doujin because it predated the Classic/Modern split!

[* This may be a lie.]

'twas at a loss for art ideas after starting on a project that's gonna take a while, then happened across the last pic I drew of these two back in 2015.