"Right, right -- the whole thing with Rose and the time-eating lizard things we knew about," Marty confirms. "And the one where Ten and Five met and kind of merged the TARDISes together and the world was going to be destroyed by something the size of Belgium. The other stuff. . .well, I guess if one Doctor's good for saving the universe, two or three have got to be even better, eh? And saving yourself from shit is something canon me knows a little about from Part II." Although in that case Marty-II had to save Marty-I from a situation Marty-II had caused. "Universe hasn't ended yet, so I think we're all good."

Doc is looking thoughtful himself. "I wonder then if what you do technically counts as crossing your timeline," he remarks to Lisa. "You almost never bump into your other selves, do you? You just happen to be in different cities all at the same time. Which, granted, is temporally significant, but about the safest way TO live through the same year over and over."