The bonus menu
Successfully complete the game on any difficulty to unlock multiple categories of options at the "Bonus" menu that can be purchased with the points earned during the game. The points are earned by collecting treasures and journal entries as well as completing optional conversations.
The available categories are:
- "Character Gallery"
- "Character Skins"
- "Concept Art"
- "Equipable Weapons" (including the Barok .44 revolver, which almost always kills with one-hit)
- "Gameplay Modifiers" (including infinite ammo and slow motion)
- "Render Modes"
Note: Using weapon and gameplay modifier/cheat options do not disable earning any trophies.
The render modes unlocked through the bonus menu in this game allow you to change the visual aspects of the game and create a whole new experience.
- ASCII Mosaic
- Thief Vision
- Negative Land
- Chalk Dust
- Rainbow Fun Land
The video below demonstrates them... and some of the other unlockable bonus modes available.
You can find a hidden bronze trophy by swimming in the water near the sunken pirate ship that you find in Chapter 12. As Nathan swims around, he'll say "Marco" and Sam will ask "Marco What?" This continues the tradition, established in Uncharted 2 and then carried on in Uncharted 3, of making a joke reference to the popular "Marco Polo" pool game.
Nathan Drake drives around Madagascar in a Jeep, with Sully and Sam. If you pay attention to the vanity plate on the vehicle, you'll see that it says "VN373." Flip that around and it basically reads "Elena," a clever little reference to that familiar character.
In Chapter 4, you'll see a sequence wherein Nathan and Elena sit down for an old school gaming session. The game being played is Crash Bandicoot, the first big title for which Naughty Dog is known, which appeared on the original PlayStation. Nathan will make an attempt to play through the first level and beat his rival's high score.
Papers, Please, a popular PC indie title, takes place along the border of the fictional country of Arstotzka. In Uncharted 4, you'll find a reference to that fictional country in Chapter 11, during a conversation Nathan has with Sully in an immigration checkpoint (Nate will make the reference).
As you play through Chapter 11, Nate and Sam will stumble across an unfamiliar portrait of a pirate that has the sigil of a monkey with a poison dagger and an hourglass. Then in Chapter 14, you'll see portraits of the founders in Libertalia's bank. One of them has most of his name obscured on the frame, but it starts with a "G." These are references to Guybrush Threepwood, the star of the classic LucasArts adventure titles set on Monkey Island.
In 2015, when Naughty Dog was supposed to demo Uncharted 4 at the E3 convention, a cutscene played and then Nathan Drake stood around at the edge of a marketplace, doing nothing. The presenter had failed to find a controller. Now, as you play Chapter 11, you'll witness the cutscene and then Nathan Drake appears in the familiar location. Don't do anything for around 30 seconds and you'll receive a special trophy, which doubles as an Easter egg.