There are several synonyms for the phrase "dash of madness", which is often used to describe a small amount of eccentricity or unpredictable behavior. Some possible options include "hint of lunacy", "whisper of chaos", "pinch of insanity", "trace of dementia", or "smidge of delirium". Each of these phrases conveys a slightly different nuance or flavor, but all suggest a touch of unpredictability or irrationality. Whether used to describe a theatrical performance, a wild party, or an unconventional personality, these synonyms can add a lively and evocative element to any piece of writing or conversation.