Xenu apparently IS connected to Stan Lee. Stan Lee, Larry Lieber and Jack Kirby created Zemu/Xemu (what I'll call Stan Lee's Xemu) in Strange Tales I#103, December 1962. This third person is the Jack Kirby who created Xemnu (what I'll call Jack Kirby's Xemnu), see below, an apparently different villain.
* * OT3 compared to Stan Lee's Xemu * * OT3: Name Xenu or Xemu | Stan Lee: Zemu, changed to Xemu in Fantastic 4 I: #158
OT3: From alien planet | Stan Lee: from alien planet
OT3: The head of the Galactic Confederation | Stan Lee: Warlord, former ruler of the Fifth Dimension
OT3: Came to earth | Stan Lee: came to earth
OT3: Imprisoned | Stan Lee: imprisoned
Otherwise plots are quite different.
Detailed Stan Lee plot summaries at
http://www.marvunapp.com/Appendix/xemu.htmOT3 compared to Jack Kirby's Xemnu (actually created by unknown author, Jack Kirby and Dick Ayres) in Nov 1960, reprinted in 1967 (right before OT3 was written by LRH)
OT3: name Xemu or Xenu | Kirby: Xemnu
OT3: from alien planet| Kirby: from alien planet
OT3: Xenu implants memories into body thetans | Kirby: Xemnu has powers of telepathy, telekinesis, hypnosis, possession
LRH writings, not OT3: prison planet | Kirby: prison planet
Otherwise plots are quite different
Detailed Kirby plot summaries at
http://www.marvunapp.com/Appendix3/xemnuthetitan.htmThe above two marvel-fan sites link to each other and insist that Xemu and Xemnu are different villains. Marvel's official site has no summary of Xemu, but does have a brief summary of Xemnu at
http://marvel.com/universe/Xemnu