#four doctors

Because Twelve calls Ten ‘Bambi’, ‘Baby Doctor’, ‘Manic pixie Dream Doctor’ (Twelve also referred to himself as ‘Daddy’ in that particular moment saying ‘Daddy’s home’), yells at him saying that Ten shouldn’t show off because Twelve isn’t impressed, says he has an excited puppy dog routine.

Ten is annoyed and at times angry with him. Calls Twelve ‘me with the eyebrows’, ‘granddad’ and is worried about Twelve even existing because that meant things changed because he shouldn’t exist.

And yet they respect each other. Twelve broke the laws of time to give Ten a warning and a solution to his problem. Twelve gives him orders and Ten actually listens to a point. Ten says he is going to like becoming Twelve.

Four Doctors:

Vortex Butterflies:

The Lost Dimension:

four doctors (comic: 2015)

So the main conceit of "Four Doctors" is that the Voord have used a continuity bomb to find alternate timeliness where The Doctor made the wrong choice and didn't save the world, in order that an alternate 12th Doctor can become their leader. For Ten it's letting Wilf die in the radiation chamber, for Eleven it's choosing not to let River kill him and settling down in the universe where all of history is happening at once, and for Twelve it's when Clara betrays him and instead of going to save Danny Pink he kicks her out.

The reason the Voord chose Ten through Twelve is that they had to be Doctors who had survived the Time War (as the Voord became incredibly advanced during the war) but the Doctors question why Nine isn't there. At the end they see Nine in a café (he doesn't see them) and Twelve concludes thus:

Four Doctors (2015) by Paul Cornell and Neil Edwards (comics short)

I like how the Doctor comes up for nicknames for their other generations.

Ten calling Twelve Mr. Grumpy.

Twelve calling Ten ‘Baby Doctor’