It is found that atoms of lithium and carbon can be encapsulated in C-36 on the basis of the calculation of their encapsulation energies using density functional theory. Specifically, they can be encapsulated in C-36 better than in C-60 despite the smaller (70%) cavity size of the former. In C@C-36, the encapsulated carbon atom forms covalent bonds with the carbon atoms of the cage, which is in contrast with the case of N@C-60. Two isomers are expected to be in an equilibrium which involves spin quenching and generation. Li@C-36 and C@C36 are expected to exist in the form of dimers with nonendohedral fullerenes, i.e., as Li@C-36-C-36 and C@C-36-C-36. Three stable isomers were found for the former (A, B, and C). Equilibrium between A and C as well as that between B and C is accompanied by spin transfer between two fullerene units, while that between A and B is not. The two stable isomers in C@C-36-C-36 form an equilibrium accompanied by spin quenching and generation, allowing the dimer to be potentially useful for molecular devices.