The boot-up screen on the Pip-Boy shows that it has a "64k Ram System" with "38911 Bytes Free," identical to the boot-up screen of the Commodore 64.
Contributed by ThisGuyInTheSuit
The trailer for the the official Fallout 4 Garden of Eden Creation Kit (or "GECK") mod features a Giddyup Buttercup power armor suit called "Horse Armor". This is an intentional jab at Bethesda's own horse armor DLC for The Elder Scrolls IV: Oblivion, which was notorious for being poorly received by the gaming community.
Contributed by Psychospacecow
Attachment
The NPC Evan in the DLC Nuka World was created as a tribute to the older brother of a Fallout fan who goes by the username NoohjXLVII, who had passed away. NoohjXLVII wrote about Evan's in-game dialogue that “The words they use sound exactly like him, however he was also a pretty funny guy, full of puns,”
Contributed by KnowledgeBase
In the Japanese dub of the game, Takahashi in Diamond City is voiced by Shinji Mikami, the creator of the Resident Evil series.
Contributed by Liraxus
The games files contain unused, cut or unfinished weapons. Among these are;
•A mesh for a Ball-peen hammer, which was intended to be used as a weapon.
•An untextured, high-poly model of a kalashnikov rifle, similar to the Chinese assault rifle, as seen in Fallout 3.
•A rough Harpoon gun composed of Syringer and Assault rifle parts.
•A pistol variant of the cryolator.
•A mortar.
•A cannon which fires nuclear bombs.
•A pipe shotgun receiver, a shotgun variant of the other pipe weapons seen in game.
Contributed by Psychospacecow
A Vault 101 jumpsuit can be acquired via console commands, but it does not appear anywhere in the game otherwise. This jumpsuit's vault number is the same one that the protagonist of Fallout 3 starts in.
Contributed by Psychospacecow
NSFW - This trivia is considered "Not Safe for Work" - Click to Reveal
There is a mistake in the dialogue when the player encounters Spoiler:the Vault-Tec Rep (as a ghoul). When he talks about Codsworth, the subtitles read: "Trimming those fucking hedges like nothing happened" However, the voiceover actually says: "Trimming those damn hedges like nothing happened".
Contributed by Smirkytrick
The Globes found throughout the world have a number of errors in relation to the Fallout timeline.
•The United States and Canada are depicted as separate countries.
•The European borders reflect the real world.
•The Soviet Union is split into its former-Soviet states.
•China's land claims are not depicted.

In addition, the Mediterranean and Black Seas are shown as land masses, rather than bodies of water.
Contributed by Psychospacecow
The male player character was part of the 108th Infantry Battalion, the same battalion that Spoiler:had soldiers abducted by the Zetans in Fallout 3.
Contributed by Psychospacecow
The companion, Curie, is named after Marie Skłodowska Curie, the physicist and chemist that discovered radioactivity. She is also the first person, and only woman, to earn 2 Nobel prizes in two different categories.
Contributed by Psychospacecow
The Leader of The Brotherhood of Steel, Elder Maxson, originally appeared in Fallout 3 as "Squire Maxson", a minor character that could be found in the Citadel.
Contributed by Psychospacecow
There are a number of references to the 1982 film Blade Runner, both in the form of easter eggs as well as Spoiler:inspirations in the game's overall story:

• On top of the Mass Fusion Containment Shed building, there is a dead Raider wearing a duster and a dead Synth. The two bodies are posed similarly to Rick Deckard and Roy Batty in the "Tears in the Rain" scene from Blade Runner.
• The Power Noodles stand in the center of Diamond City, along with the Noodle-serving Protectron named Takahashi is likely inspired by the noodle stand and it's japanese-only speaking owner that Deckard eats at in Blade Runner.
• The town of Covenant requires a psychological "G.O.A.T Test" before it can allow newcomers in. Spoiler:The reasoning behind it is to tell who is a genuine human and who is actually a "Synth", very similar to the Voight-Kampf Test's done in Blade Runner, which is done to expose if the person being tested is a Replicant or not.
Spoiler:A good portion of the game's plot/backstory involves the "Synths", who are inspired by the Replicants from Blade Runner, in the sense they can mimic humans almost perfectly and hide among them. There are even runaway Synths trying to find freedom, similar to the runaway Replicants Deckard is tasked to find in Blade Runner.
Spoiler:Nick Valentine is arguably a product of inspiration from the movie, as he fits the "neo-noir" motif of Blade Runner.
Contributed by G-Haven
Codsworth, the players robotic butler companion, is able to say over 1000 English names in his dialogue, and refers to the player character as miss or mister, depending on the characters sex.
These include common English names, comedic names, and even crude ones. If the player chooses a name that Codsworth doesn't recognize, he will refer to male characters as "sir" and female characters as "mum" instead.
Contributed by Makzu
Attachment
Imgur user GatorMacheteJr sent Bethesda 2,240 real bottle caps in hopes of getting a copy of Fallout 4. He was then contacted by Bethesda Global Community Lead Matt Grandstaff via email stating that they would honor his purchase and he would get a copy of Fallout 4 when it was released.
Contributed by Pogue-Mahone