A drill guide fixture may be configured to prepare a skull for attachment of a cranial insertion fixture. The drill guide fixture may include a central drill guide and a bone anchor guide at a base of the drill guide fixture. The central drill guide may define a central drill guide hole therethrough, wherein the central drill guide hole has a first opening at a base of the drill guide fixture and a second opening spaced apart from the base of the drill guide fixture. The bone anchor drill guide may define a bone anchor drill guide hole therethrough, and the bone anchor drill guide hole may be offset from the central drill guide hole in a direction that is perpendicular with respect to a direction of the central drill guide hole. Related cranial insertion fixtures, robotic systems, and methods are also discussed.