The existence of actinide-actinide (An-An) bonding interactions has been a controversial and actively researched topic in inorganic chemistry for many years. Calculations for An-An interactions inside fullerene cages (endohedral fullerenes) typically conclude that the weak interactions observed are the result of compression due to the presence of the carbon cage but these results and interpretations fail to address the mechanistic implications of the conclusions because they don't address the reasons why two An atoms would find themselves trapped inside a cage if they don't really like to interact with each other. How can we understand the prevalence of so many An-An@C_2n as well as An-M@C_2n endohedral compounds, some of which are obtained in very reasonable quantities, if there is no real driving force for their simultaneous incorporation inside the carbon cages. In this work we will present experimental and theoretical results that together show that there are reasonable metal-metal interactions inside these endohedral structures.