9. The Fifth Doctor To The Sixth Doctor
Another slightly trippy regeneration now. The Fifth Doctor's swansong The Caves of Androzani is often touted one of the all time greatest Doctor Who stories, and rightly so. In the final moments of the story, the Fifth Doctor and Peri have succumbed to spectrox poisoning and barely make it back to the TARDIS in time for the Doctor to bravely sacrifice himself and save Peri's life by giving her the last of the bat's milk antidote. A sudden transition, this scene serves as a reminder that regeneration can be a particularly troubling and uncomfortable experience for a Time Lord and Colin Baker's frenetic, prickly introduction reminds viewers of how such a traumatic change can seriously affect a Time Lord's mind and personality. The quick regeneration and the abrasive nature of the Sixth Doctor makes for a jarring transition which, unfortunately, alienated many viewers. https://www.youtube.com/watch?v=qvAenK95PfQ