On the first level of Halo: Combat Evolved, a bulletin board can be found in three locations on the UNSC Pillar of Autumn. One adjacent to the bridge's entrance, once more in the mess hall, and the last behind a pillar in one of the ship's corridors. There are two unique versions of the bulletin board featured within Halo: Combat Evolved and in its 2011 Anniversary edition.
Halo: Combat Evolved
There are actually more bulletin boards on the Pillar of Autumn, one being found on the mission, The Maw, where there is a shattered board right through the cafeteria alongside two medical packs and an empty shotgun, but the first is the only one with legible messages.
One post on the board says: "Missing: Calico Cat: Answers to Jonesy" This is a reference to Alien and Aliens, two movies that Halo draws inspiration from, to include the banter of a Marine soldier. Jones, sometimes called Jonesy, was a Calico cat in the series and was a survivor of the first movie, along with Ripley.
There is a picture of Earth from the Moon with the caption "Fight for Her" on it. This is likely a propaganda piece that was disseminated by the UNSC. It also shows Africa, which may be a reference or foreshadowing to where the Ark's portal is hidden.
There is also a note reading:
Pentium XI 33 GF
*7 Speed Manual transmission.
Hyde Park Condo
There is a sign that says: "Marines keep it clean! Clean your area, toss your filth, put away your trash." The term "Keep it Clean" would later become the catchphrase of a Halo 3: ODST character, the Superintendent, and is the name of a trailer for the game.
Another says: "Duty roster Pillar Of Autumn" with some illegible writing which is supposedly the duty roster.
One says: "Marines scooters are for squirts, no scooters on deck."
Another reads: "Attention marines, callbacks for South Pacific" and the rest is cut off by a keyboardish item. It is likely that this is a reference to the musical, South Pacific.
Halo: Combat Evolved Anniversary
Appearing within the same location as Halo: Combat Evolved, the board features new messages, new Easter eggs, a technologically upgraded appearance, and new references to Halo media. The board features a bar with the options "File, Edit, Object, Window, Help."
One of the posts parallels the original version of the board's notice alerting that Jonesy is missing with a "cat found" poster referencing an Internet meme in which the "cat" in the notice's photo is clearly an opossum. The handwritten poster reads:
Light tan w/ black and grey
- No collar
- Not very friendly, I think she might be scared
- Not house broken either :(
- Found on 75th
- If she's yours, call Dan 714-[redacted]
Next to this post is a notice asking "Have you seen my goose? He is missing. Reward offered." This is another reference to Jonesy. In the picture, the goose has laid a golden egg.
Another one of the posts displayed on the board includes a distinct reference to Requiem, which was first seen within Halo 3's ending and later featured more heavily in Halo 4. The poster advertises "Sneak Preview Night" to a new film called Dark Planetoid Rising - "7pm Friday, Aft Theater [No reserved seats]" - a reference to a 2008 NeoGAF meme. The poster for the advertisement is a direct screenshot of the Legendary planet.
A notice below that displays a promotion for a band called Fist of the Unicorn:
Special encore performance by ship's band
Fist of the Unicorn
Featuring: SPC Van Kalletta on lead guitarz
(and replacement drummer PFC Dimitrov)
Rockin' your Eridanus off
Saturday 1600 hours
The Defiant Map Pack's promotional image can be seen within the top-right corner, declaring "Defy the Covenant", in parallel to the original propaganda poster.
Beneath that a small poster advertises:
Work 4 Hire
The final poster is an order to the crew.
To All Crew Members:
>>All unit VTARS must be submitted for final approval by 0700 every Tuesday.
Units in VTAR noncompliance will be subjected to additional review by <FRANCH INSPECTOR>.
Maj. Cammarano <<
This notice will serve as your final reminder.