- Actor Allusion:
- It hardly seems like a coincidence that Jennifer Hale voiced a redheaded female super-soldier with the rank of commander. Halo 5: Guardians even reveals that Palmer has an alien with a crush on her!
- Japanese dubbing example. Before vocing Cortana, Ayumi Fujimura voiced Fi, a character that plays a similar function to Cortana.
- B-Team Sequel: The first Halo game to be created entirely by 343 Industries, not Bungie.
- Development Gag: The UNSC Infinity is yet another one to the Halo franchise's Spiritual Predecessor, Marathon.
- Fanfics upon fanfics had been written after Halo 3 centering around Cortana finding some kind of cure for her rampancy, such as gaining a body or being transferred into some kind of Forerunner supercomputer. Halo 4's answer? Reality Ensues and she dies from her rampancy. A large amount of those fanfics also involved her becoming evil and opposing John. Aside from a few sections where she goes mad and delays the mission, she never turns openly against John and remains your ally through the end of the game. That said, given that all the above-mentioned theories ended up being confirmed in Halo 5, it looks like those fanfics were simply set one game too early.
- Many posts speculated on the Precursors being the game's new enemy, when it's actually the Forerunner Prometheans. Also made moot with the reveal that the Flood are a mutated version of the Precursors, making them not a new enemy anyways.
- Prop Recycling: Of a single-work, single-level example, though it is so subtle that it is practically unnoticeable. In the level "Reclaimer", the Mammoth includes an amount of textures and geometry shared with other human vehicles and weapons, only exploded and scaled. For examples, the wheel mountings share color-shifted textures with the Warthogs, and the hand rails in the interior catwalks use geometry from battle rifles. This was not done out of laziness, but necessity, since the level was just so big that they had to use these ways of stretching the memory budget as far as they could due to the finite memory of the Xbox 360 console.
- Stillborn Franchise: Not Halo itself, but the Spartan Ops spin-off, which never progressed past a first season. Overall reception to the first season was lukewarm, with much debate about it replacing Firefight, its level design, the storyline, and the lack of Master Chief. They ended up having to end it by completely destroying its setting of Requiem, with Halo: Escalation being forced to pick up the unresolved plot threads, such as Fireteam Majestic's fate (DeMarco dies, Thorne becomes the new leader, and they get a new member) and the battle between Infinity and the Covenant over the Janus Key (a Forerunner AI ends up taking it away from both sides).
- Word of Dante: The game's article in Official Xbox Magazine claimed the new Covenant splinter faction was called "the Storm", but this turned out to be a mistake stemming from the lowest ranks being called "Jackal Storm" or "Elite Storm", etc. In-game, the faction is only referred to as "the Covenant" as before. However, many have taken to calling them "the Storm" anyway, to differentiate them from the previous empire.
- What Could Have Been:
- David Anthony Pizzuto was the original voice for the Didact, but unfortunately he died before he could finish recording.
- Originally, episodes of Spartan Ops would have been accompanied by a stylized motion comic instead of the final photo-realistic CGI cutscenes.
- The Mammoth was originally conceived as being a much more literal Base on Wheels in its original concept as the "Tortoise" deploying into a siege-mode with bracing pistons, a raising sniper nest, and a deployable landing pad which accommodated a Falcon.
- Concept art reveals that Drones were at one point considered for inclusion, including a sniper variant.
- Gek, The Dragon of Spartan Ops, was originally going to get his own subplot, but it was cut for time.
Trivia / Halo 4