We report on an extended series of Mossbauer measurements on noble-gas (Ar, Ne, Kr, and Xe) and alkali (Rb and Cs) inclusions in Mo and W. Using TEM on some samples allowed a direct size distribution measurement. The sites occupied by the Xe-133(Cs) probe atoms differ for small atomic rare-gas (Ne and Ar), large atomic rare-gas (Kr and Xe), and alkali inclusions. We followed the site population and inclusion sizes as a function of annealing temperature, observing the expected growth of the inclusions upon annealing due to distinct growth mechanisms. Temperature-dependent measurements show that two kinds of inclusions are formed: soft ones with a characteristic temperature which is too low to make them contribute to the Mossbauer spectrum and tough ones which are perfectly embedded in the matrix. Kr and Xe inclusions of the latter kind feature a characteristic temperature which (i) is remarkably independent of preparation conditions and (ii) greatly exceeds the largest possible value for pure rare-gas solids. We argue that this kind of solid rare-gas inclusion ''borrows'' its dynamical properties from the high Debye temperature matrix.