The structure and vibrational spectrum of the novel endohedral fullerene Y2C2@C-92 was studied by Raman spectroscopy, with particular emphasis on the rotational transitions of the diatomic C-2 unit in the low-energy Raman spectrum. We report evidence for tunneling of this unit through the C-2 rotation plane and observe anomalous narrowing in a hindered rotational mode. We also report complementary density functional theory calculations that support our conclusions and discuss potential applications to quantum computing and nonvolatile memory devices.