During the first parts of the difficult regeneration, the Doctor started to revert to his prior personalities. He mistakenly referred to his current companions as previous companion names (He called Adric "The Brigadier" and "Jamie" and he called Tegan "Vicki" and "Jo"). He mentioned Romana, as if she were a current companion, yet she had previously departed during the Tom Baker years. He also urged Tegan not to reverse the polarity of the neutron flow which, as every fan will know, was a popular line from the Third Doctor. He showed the characteristics of the First Doctor when he called Adric "boy" and had a very similar laugh to that of William Hartnell, too. He also picked up and attempted to play a recorder for a few moments before setting it aside again. The range that Peter Davison showcased in these scenes was excellent as it was a way to hark back to the days of old Doctors. It shows that what he said a few years later in The Five Doctors was spot on, that "a man is the sum of his memories, a Time Lord even more so". This was one of the first occurences of the Doctor reverting back to previous incarnations, something that has been explored quite a few times in NuWho, specifically with Matt Smith. The companion confusion is sure to remind fans of the more recent first episode under Peter Capaldi's belt, Deep Breath, in which he confused Clara and the Pasternoster Gang with his bizarre post-regnerative outbursts. Perhaps the Doctor really should take that holiday that Romana kept reminding him about.