Uncharted 2 reference
In Chapter 2 Breaking and Entering, when Flynn lifts Drake onto a roof he says "You put on weight mate" and "Whew, alright, No more doughnuts for you".
Doughnut Drake is a massively overweight version of Nathan Drake. His voice is also much deeper than Drake's voice.
How to Unlock
In Among Thieves, Doughnut Drake can be bought in the single-player skin store. He can also be purchased in the multiplayer store for the expensive price of $2,000,000. In multiplayer, he can only be purchased after the player has reached level 60 (X).
In Drake's Deception, can be unlocked on the Monastery Co-op adventure hard or crushing mode. (The hematite skull bead treasure is no longer glitched, as of the 1.04 update in early February 2012)
Also can be unlocked by beating the remastered versions of Uncharted Drake's Fortune,Uncharted 2 Among Thieves & Uncharted 3 Drake's Deception on the normal difficulty