If the series were to end forever, heresy I know, I'd like the Doctor being a paradoxical closed time-like loop, perhaps created by the universe itself as an error correction mechanism for underlying hypercomputation in branchial space.
Closed timelike curve - Wikipedia
Hypercomputation - Wikipedia
Finally We May Have a Path to the Fundamental Theory of Physics… and It’s Beautiful—Stephen Wolfram Writings
	
		
			
		
		
	
				
			Closed timelike curve - Wikipedia
Hypercomputation - Wikipedia
Finally We May Have a Path to the Fundamental Theory of Physics… and It’s Beautiful—Stephen Wolfram Writings
 
				 
 
		 
 
		 
 
		 
 
		 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		