the feathers/fur/sparks will fly

the fur will fly

there will be serious, perhaps violent, trouble. informal
This phrase originated in the early 19th century, in the US. The image is of a furious fight between dogs or cats.
See also: fly, fur, will

the ˌfeathers/ˌfur/ˌsparks will ˈfly

(informal) there will be anger, annoyance, etc: The fur will really fly when she tells him he can’t go out tonight.
See also: feather, fly, fur, Sparks, will