The first part of the article focuses on how an accident or unexpected event may influence a performance piece. Examples of accidents with creative potential are described. The second part concerns improvisation; it investigates what it means to improvise in performance art and reveals the political potential of improvisation. Even though artists reluctantly admit they improvise or make errors, examples of such cases suggest this is not uncommon and usually involves unexpected audience interaction or occurs when the piece's structure is open. The article is based on artists' statements, performances described in the literature, and those witnessed by the author. The theoretical part is mainly based on articles by Alessandro Bertinetto.