Despite being Water (Or Mutated Chao) slime sounds

(Advance 1) Angel Island Zone.

Originally for Infinite Battle Now retooled

2/3 of them are references to

Sonic's Concept and is also a Skin in Sonic Superstars Cream's Debut (Though inconsistent looks)

A former 90s rival's (A red capped plumber guy) recent 3D platformer since 2017

The 3 Promotional Avatars wearing Rain Boots / Wellies

Basically

Valgallah's Cream's "Chao Force" Super

Command is

D,DF,F X+Y

(coming some time soon or something.) The 1st Sonic Battle Redux arcade Run: Sonic.

Yoshi and Birdo cosplaying as Ichigo Momomiya

Possible fang/nack sprite sheet? (And nic the weasle (From the comics)

Act Music as Rounds? (may not apply to every stage)

I'm taking you down like its 1998/1999!