  We report on strong pretransitional effects across the isotropic
liquid-plastic crystal melting temperature in linear and nonlinear dielectric
response. Studies were carried out for cyclooctanol (C8H16O) in the
unprecedented range of temperatures 120 K < T < 345 K. Such pretransitional
effects have not yet been reported in any plastic crystals. Results include the
discovery of the experimental manifestation of the Mossotti Catastrophe
behavior, so far considered only as a hypothetical paradox. The model
interpretations of experimental findings are proposed. We parallel the observed
pretransitional behavior with the one observed in octyloxycyanobiphenyl (8OCB),
typical liquid crystal (LC), displaying a reversed sequence of phase
transitions in orientational and translational degrees of order on varying
temperature. Furthermore, in its nematic phase, we demonstrate first-ever
observed temperature-driven crossover between regions dominated by isotropic
liquid and smectic A pretransitional fluctuations. We propose a pioneering
minimal model describing plastic crystal phase behavior where we mimic
derivation of classical Landau-de Gennes-Ginzburg modelling of Isotropic -
Nematic - Smectic A LC phase behavior.
