I do not think you should yell at them for pooping. All I think you should do is just clean it up. I hope this information helps. If it does not just email me and i will give you another anwser.
Don't punish it for pooping. Everybody has to, even Tamagotchis!!! But, if you catch it on time, you can make it go on the toilet by going to the toilet icon when you see the waves coming from its body.
Tip: Some Tamagotchis don't have the waves come from its body.
go to the toilet icon and itll clean up. did i help? o and BTW how do u do colors in ur siggie cause i tried to to the programmed color thing and it didnt work TT^TT <_<