The phrase "go kooky" can have various synonyms based on the context of its usage. Some of the synonyms for this phrase include going crazy, losing one's mind, going off the deep end, losing one's marbles, going bonkers, flipping out, losing one's cool, going haywire, going berserk, and losing one's grip. These synonyms can be used in different situations to describe an individual's unstable behavior, whether it's due to anger, stress, or mental instability. All these words can convey an overwhelming sense of being out of control, and it's essential to choose the right synonym based on the context of the situation.