There is a cover of Xemu together with the words "macabre" and "Invaders of the Fifth Dimension" which has been suggested to have been an inspiration for Hubbards OT III story and his scientology space opera. Hubbards e.g. talks about "the Marcabs" (derived from macabre?) and "The Fifth Invaders" (derived from Invaders of the Fifth Dimension?) in his lectures and books, as well as Xenu. On Philadelphia Doctorate Course (from 1952) I have found that he talks both about "Fifth Invaders" and "Markab" (or Marchab, a star with the real name Alpha Pegasi) so he could not have gotten those ideas from that cover since the comic figure Xemu first appeared in magazines in Nov 1960. The name Xenu is of course still somewhat open to speculation.