Board Thread:Off Topic/@comment-13199219-20130821205109/@comment-198.174.0.11-20130915164110

198.174.0.11 wrote: The TARDIS is capable of traversing between alternate universes. What if the Doctor accidentally traveled to this universe and wound up on this planet and started helping this species recover from the onslaught of the monsters, unknowingly creating an evil clone of himself on the parallel world the monsters were swarming from. When he found out what had happened he tried to leave, but the clone stowed away on the TARDIS, knocking the real Doctor out and dumping his body on Gallifrey before heading off the the TES reality to impersonate Tiber Septim, whom he disposed of in a black hole.

This could have happened in the Doctor's younger days.