There are many philosophies and theories on what creativity is and how it works, but one popular idea is that of variations on a theme and intersection of concepts. This literature review explores philosophical proposals of how creativity emerges from variations on a theme, and how formalizations of these proposals in human subject studies and computational methods result in creativity. Specifically, the philosophical idea of intangible clouds of concepts is analyzed with empirical studies of concept representation and mental model formation, and mathematical formalizations of such ideas. Empirical findings on emergent neural activity from neural network combinations are also examined for evidence of novel, emergent ideas from the collision of existing ones. Finally, work on human-AI co-creativity is used as a lens for concept collision and the effectiveness of this model of creativity. This paper also proposes directions for further research in studying creativity as variations on a theme.