Okay. So. What if the flower thing was the result of Flynn trying to do the turn-time-lord-into-human thing but it got flung out of the TARDIS and turned into the flower. Flynn then traveled several years into the future, and started his human life. And Rapunzel was a kind of half-timelord thing like River and when Flynn got stabbed there was just anough timelord between them to bring Flynn back! <--- YES. head canon accepted.