A variety of identity disturbances has been described in psychiatric patients. Although such disturbances possess some common features linked to shared or core psychological structures, qualitative differences that allow them to be distinguished from one another also exist. The cases reported are intended to draw attention to a severe and striking type of identity disturbance observed in psychotic patients, for which we have proposed the eponym, ‘the Zelig phenomenon’. The discussion focuses upon the issue of the coexistence in psychopathology of continuity and discontinuity. This apparent paradox can be regarded as an example of parallax, in which two quite different, yet equally valid, perspectives are possible and may be brought alternately into play. It is, however, argued that in the delineation of psychopathological entities it is necessary to adopt the perspective that considers discontinuities and matters of form, even though they may be at times overshadowed by continuities that derive from the alternate perspective.