>>36334067
It's between Flowey-Fubuki and Flowey-Flare. I forget what it was exactly, but I remember her being in a collab, I think with Flare and Coco, and the losers had to put poop on their streams for some period of time. I thought that was what happened, but I don't remember the context or when it was. Regardless, that's in the past.
But it seems as of her third RE2 stream (July 25) she's had poop on most of her streams. It's always in the bottom left corner above the controller symbol. If the overlay doesn't have that controller symbol, there's no poop. However, it would appear that 3 days ago she added the poop to her Undertale overlay, too.
I don't remember where this is from or why it's appeared recently.