Bulletin board

On several Halo: Combat Evolved levels, a bulletin board can be found just outside the bridge of the Pillar of Autumn. Some of the messages look plausible, some are just silly, others are Easter eggs.

One says: "Missing: Calico Cat: Answers to Jonesy" This is a reference to Alien and Aliens, two movies that Halo borrows from many times, to include the banter of a Marine soldier. Jonesy was a calico cat in the series, the only 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 propaganda within the UNSC. It also shows Africa, and may be a reference to where the Ark's portal is hidden

There is a note reading:

For Sale: Pentium XI 33 GF Chicago Office Colony Ship *3 Speed Manual *Transmission Hyde Park Condo Integrity

This is a reference to Bungie being bought by Microsoft. It mentions the location of Bungie's old office, as well as referencing a stage in Marathon, entitled Colony Ship for Sale: Cheap.

There are other things too. Some you can read, others you cannot. Also you can see the words "Marines Keep it Clean" and "Scooters are for Squirts, No Scooters on Deck".

Another says "Attention Marines callbacks for South Pacific". The bottom of the poster is cut off by the keyboard.