'But...What if?' is about the relationship between 2 personalities. On the one hand, there is Balloon Brain, who is impulsive and creative and therefore very sensitive to the constant stimuli of daily life. Balloon brains is full of ideas and plans and would like to implement as many of those ideas as quickly as possible out of enthusiasm. On the other hand, there is Cube Head who, instead of enthusiasm and spontaneity, is full of concerns about the ideas and choices being made. This creates uncertainty, resulting in many of these plans being dismissed and enthusiasm extinguished. Despite this duality, the characters will still have to find a way to live together.