Go with Roxie to the Giant Changing Room Alice & Roxie in: GYM RAT chapter 2 by Marak077

Alice and Roxie entered the changing room for giant animal girls. Rows of gigantic lockers scattered about, massive benches she could walk from one end to another on days endlessly, and there's a room for a shower and one for a sauna. Roxie shipped her membership card on one of the lockers in front of the bench and promptly undressed to get wear her gym wear, which Alice took que to do the same. They flush each other with a red cheeks smile seeing both of their naked bodies.

Just as she and Alice finished dressing up. Roxie felt a little unwell on her stomach, "Ugh, I need to go to the bathroom. You mind staying here while I do business?" Alice gave her a thumbs up, "Thanks!" And promptly did her business.

The Mousegirl sit down, and waits, unaware that just as she's at least relaxed and put her gym stuff with Roxie's, a gigantic form is about to step in and would ruin her day. Who is it?