Random ideal but perhaps Rarity in
https://diaperedanime.com/forum/showt...6/index10.html could perhaps have a scat and water sports fetish and Rarity swears/curses leading Spike to make a remark that gives Rarity the ideal to have Spike use her as a toilet(I'm going with the Spike in that rp has a tiny bit of control so it's possible) whenever shes bad/naughty and she makes sure to do it when shes sure Spike could use her