We use three-dimensional classical molecular dynamics to simulate femtosecond time-resolved experiments on the caging dynamics of I-2 in rare gas environments [Wan , J. Chem. Phys. 106, 4353 (1997)]. The calculated pump-probe signals are in excellent agreement with experiment. Prominent oscillatory structures as observed in the pump-probe signals are interpreted in terms of caustics which appear in the classical bound state dynamics of the caged molecules. The results confirm conclusions based on a simple statistical model which treats the collisions as random perturbations involving hard sphere scattering.