We consider special topics related to the Casimir effect [1]. We extend the considerations of the fluctuations of the Casimir pressure [2], [3] to finite temperature [4]. In the unphysical high-temperature limit the Green’s functions become more singular. This explains why these Green’s functions allow the determination of the Casimir pressure in this limit, but not of its fluctuations. We remark, that the boundary conditions for conductors in classical Electrodynamics are not sufficient for a unique definition of the Green’s functions.