Doctors' First Episodes

We begin our second season of "Time & Space" eagerly awaiting the arrival of the Thirteenth Doctor! Jessica and Phillip get ready by dissecting the first episodes of "new" Doctors. They look at how each episode handles newly regenerated Time Lords - taking their first confused steps, how new companions get introduced, and how we establish each "new" Doctor as being part of the long-established line/franchise.

In their look into the TARDIS library, the couple reviews the Big Finish release of "Class, Vol. 1" (learn more at https://www.bigfinish.com/releases/v/class-volume-01-1857). Does this cancelled spin-off improve as an audio adventure?

What's your favorite "first episode" of a Doctor?