From Halopedia, the Halo wiki
Craig is an internet meme originated from an infamous screenshot of a Jiralhanae Berserker from the Halo Infinite Campaign Gameplay Premiere. A series of Easter eggs that reference Craig can be found in Halo Infinite.
Following the release of the Halo Infinite Campaign Gameplay Premiere on July 23, 2020, a screenshot from the trailer, depicting a Jiralhanae with a deadpan expression moments before being meleed by John-117, began circulating on Twitter. Users started calling the Jiralhanae in the screenshot "Craig", with 343 Industries Community Director Brian Jarrard endorsing the meme on the next day. Phil Spencer, the head of Xbox, jokingly called Craig the "new official Xbox mascot" on Twitter.
After 343 Industries announced that the release of Halo Infinite would be delayed from 2020 to 2021, Craig was again brought up in the October 2021 issue of Inside Infinite on Halo Waypoint. Character & Combat Director Steve Dyck cited "Craig" as representative of "some content and systems that were not ready" for the showcase, and noted that the delayed release allowed the Character Team at 343 Industries to make improvements to the facial design. In the same post, Character Art Lead Bryan Repka mentioned that Craig has "picked up a new hobby and has done well for himself", alluding to the Easter egg at the top of Tower, which shows a poster of Craig as a musician touring the Banished outposts and bases. The comparison between the original screenshot and an updated face of a Jiralhanae from the Inside Infinite issue was later posted on the official Xbox Twitter account as a "How It Started vs. How It's Going" meme.
Following the release of Halo Infinite, Craig was among the characters featured on the official Halo-themed Valentine Day cards released on February 14, 2022. He was also mentioned in the description of the Flash Fjord armor and vehicle coatings.
One of the marine's idle dialogue references Craig: "I saw this one Brute — weeeird look in his eyes, (Chuckling) like, really deadpan. You could tell, he'd seen some stuff in his day, man. Umm, I wonder if he had a name. I almost want to call him, like, y'know, like Greg or something. Yeah, Greg. Yeah."
Tower Easter egg
The easter egg can be found on top of Chak 'Lok's Tower. It shows a stage with speakers along with a music album and a poster. The music album has a picture of "Craig" on it along with the text "Greatest Hits". It also lists the names of the songs in the album, some of which are references to jokes made about Halo Infinite and Craig's deadpan expression. The songs are titled:
A poster listing tour dates can also be found Banished base locations. The poster reads: CRAIG ZETA HALO TOUR 2560
At the Tower, you need to use Grappleshot or a Wasp to get to the top of the structure. You will most likely need the 40% cooldown reduction upgrade for this. Climb up one of the four tower supports and then grapple up over the top of the Tower. At the top you will find the Easter egg. There will also be a metal bar next to the microphone with some red paint on it. Activate it, then melee it and it will play guitar notes.