Antonyms for "crack-ups," which usually means a comical or humorous situation, could include serious or somber circumstances, unamusing or unfunny scenarios, or even frightening or alarming events. Instead of a crack-up, one might encounter a solemn or sobering experience, a situation devoid of humor, or a situation that is scary or unsettling. Some antonyms could be catastrophic events or traumas that are emotionally distressing, rather than humorous or lighthearted. Additionally, dull or mundane situations could be antonyms, lacking the excitement or amusement implicit in a crack-up. Regardless of the antonym used, it is clear that it is essential to change the context of the word to convey a different tone or meaning.