Here's a video I would like to share with you. I retouched the Doctor's regeneration in Twice Upon a Time, because I simply don't like the Doctor's last line in it (too... Moffaty!) and instead, went with a much more fitting alternative (in my opinion). I tried uploading it on YT, but it blocked me so I upped it in dailymotion. Hope you can see it, and like it!
He originally said "Alright. Here we go. The long round," as a reference to Twelfth's remark about finding out if he survives "the long way round." Whereas what he says now evokes what he said to Susan before he said goodbye to her.
Hartnell's last words were "Stay warm?" and then he fell down and his two companions moved toward him and then watched in disbelief as direct eyewitnesses to something they still couldn't believe despite having seen it directly...
"Stay warm" was actually back at the snow base, right after "I must get back to the TARDIS!" He was scripted to say in the TARDIS (more or less) the lines we hear Bradley's One saying as we first meet him in The Doctor Falls, ("No, I won't go through with it... I will NOT change...") but they were under a time crunch and no one wanted to deal with Hartnell blowing his lines one last time.
Well, I didn't want to start another thread, but here's another fan-edit-y thing I did a while back, hope you enjoy.