The latest video in YouTuber Shesez's excellent Boundary Break series—which takes the viewer outside the boundaries in popular games—is all about Borderlands 2, and it reveals plenty of secrets about the way the world is designed.
My favorite revelation is that the flashy intros for major characters and bosses actually happen directly inside the game world, rather than being made separately. Those intro have splash backgrounds: if you zoom out, you'll find that those backgrounds just appear as textures in the world for the intro, linger behind the character, and then vanish when the intro is over. Skip to 9:30 in the video to see what I mean.
Shesez also finds weird, empty rectangles hidden far below each level, each one segmented into smaller boxes (see 7:00). What's their purpose? Gearbox senior programmer Kyle Pittman jumped on the line to explain: they're called global loaders, and they're used to transition players and their vehicles between levels. "If you travel from one map to another, and then also if you die and respawn...we take your player character and move them down to these regions. Basically this is just a way that we can get the player character out of the game world and into a safe space," he says.
It started as a solution to bugs in the first Borderlands, which Pittman also worked on. Sometimes, when players were moving between levels their vehicle would fall through the world—having an area for players to go first fixed the issue.
Shesez also finds a random model of Claptrap in a T-pose hidden underneath a mountain near the start of the game. Pittman explains that the model would've been used to scale the level around it, but that the level was redesigned to add a new hill, effectively burying poor Claptrap. The designer just never went back and deleted it, he said.
The video also reveals rainbow-colored boxes dotted around, which are used to replace assets that were removed from the world, presumably so the team could keep track of them. We also see cubes underneath the platform where the player meets Angel: these cubes are basically hidden stands for shock field generators that pop up during the Angel boss fight.
There are lots more secrets revealed in the video, which is worth a watch in full. And if you're curious, the entire Boundary Break series is here, all 147 videos of it.