When it comes to synonyms for the phrase "goes nutty", there are a variety of options to choose from. Some alternatives could include "loses it", "flips out", "goes crazy", "becomes unhinged", or "has a meltdown". Each of these options convey the idea of someone becoming uncontrollably emotional or irrational in a negative way. Other synonyms might include "freaks out", "loses their cool", "gets worked up", or "throws a fit". No matter which synonym you choose, the overarching idea is one of loss of emotional control or rationality.