going Mufasa

When a father goes off the rails kicking ass or obliterating a foe when protecting his son(s) and/or daughter(s) after they have been wronged in some way, referencing Mufasa’s brutal attack on the hyenas in The Lion King; an extreme version of “papa bear”

“Joe cheated on Cindy and dumped her, her dad found out and went full-on Mufasa on Joe’s ass!” (going Mufasa)

Mom went out for a gallon of milk

The female version of “Dad went out for cigarettes”, where the mom goes out and abandons the kid under the pretense of buying milk.

Mom went out for a gallon of milk and never came back.