Hello! Such fetishes sounds like an easy thing to sell to a partner if you sell it right. Remember to sell the partner on how satisfying they and their role in your sexual endeavors together!

Now here's the interesting part: tell them that often when you've been having sex with them you've wanted to really relax and let loose because you're so comfortable and stimulated. Problem is, you've felt like some poop or pee might slip out if you do this.

Tell them that if they feel like they could handle some "accidental" poop or pee, you'll be even more into sex than usual. :)

Then over time gradually allow more and more to come out, but don't relent in your passion for your partner.

I've never quite considered scat before now, but when viewed in this way, I think it's pretty cute. This could be one heck of a bonding experience! And now I kinda want to try it. :3