What is opened a can of whoopass?

"Opened a can of whoopass" is a colloquial term used to describe a situation where someone gets very angry or becomes very aggressive towards another person. The phrase is thought to have originated in the 1980s and became popularized in the 1990s. It often refers to a physical altercation or intense verbal confrontation. Generally, the phrase is considered to be a humorous way of describing a situation where somebody has become extremely upset or aggressive. It may also imply that the person has gained the upper hand in a fight or argument. The phrase is sometimes used in a more light-hearted, tongue-in-cheek manner as a way to express enthusiasm or excitement for something, such as a particularly exciting sports game or activity.