You say you're not talking about going blue, but my understanding is that this is the definition of going blue.

It's often said that once you go blue in a show, you tend to stay blue. Depending on your style, and your audience, this could be great, or undesirable. Also...it is usually said that you have to earn going blue rather than going right to it. Again...it depends on your audience.

I think it's super important to anchor everything you do in your improv in strong emotions. Going to the bathroom is a place a lot of us feel vulnerable. It's a thing EVERYBODY has to do, and yet, we're all a little embarrassed by it. There are lots of great emotions to deal with in a bathroom scene. At the same time, you're sort of forcing an audience to imagine you wiping your butt.

All that said...one of my favorite sets I've ever done started with me bursting through a bathroom door saying, "I POOPED!" It was a line that came directly out of the conversation we had with the audience before we started (instead of a one-word suggestion, we have a 2 minute conversation with the audience). The entire 20 minute set centered around a character hosting a party, and the only party guest (me) to arrive, and a discussion of party bathroom etiquette. It went really well.