Mad donkey shit
You throw this at someone who’s so bad at something it’s like watching a baby try to ride a bike.
You said 'Mad donkey shit' to your classmate after he failed the science test and cried.
Your sister texted you 'Mad donkey shit' because you spilled your cereal all over the floor.
Your dad yelled 'Mad donkey shit' at you for eating the last of the pizza.