My dad used to be a game programmer and he says that sometimes programmers put in easter eggs that you can only find under the right conditions, in this case,
a. the tamagotchi is alive
b. there is a poop on the screen
c. the tamagotchi just be walking around, not playing a game/connecting/ect.
other people have had their tamas eat poop, cartwheel/roll, and then there are holiday animations, like easter eggs/bunnies, talking/dancing Christmas trees and Santa clause at midnight, and i have seen a snowman around new years. my aunt said, and i quote, "They made them so much like a child, I'm amazed. One time i was watching my daughter's baby tamagotchi, and it pooped twice while i was busy, and i didn't see, and when i came back it was sick and mad and everything!"
i really like tamagotchis for this reason, among others!
it was nasty but i claned it up and it was back to normal help 
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