Starry Night

The First Halo 3 TV AD 1:00min long xZjBEtZlO20 Starry Night is a short CG spot released on December 4, 2006 as an ad for Halo 3, and intended to be used as a television commercial.

Video Breakdown
It begins with a young boy and girl lying in grass contemplating the existence of life on other planets. Who they are and where they are is unknown and up for debate. The boy turns to look at the girl, but instead sees the Master Chief's helmet laying on the ground.

It suddenly transitions to the Master Chief's point of view, with the sound of the two kids screaming merging into a Wraith's mortar detonating. The Master Chief is laying on the desert floor looking at his fallen helmet. The Master Chief gets up and various voices are heard in the background as he puts it back on and picks up his dropped Assault Rifle, and we see what appears to be a destroyed Mongoose flipped-over behind him.

After clipping the weapon on his back (it seems to be held by magnets), he uses a device, temporarily known as a "Shield Grenade", to protect himself from an incoming plasma mortar, which destroys the overturned Mongoose in front of him. The Chief takes off running and holsters what appears to be the M6D Pistol from Halo 1 and detaches the Assault Rifle from his back. He jumps over a ledge to combat Brutes dressed in new armor, and redesigned Wraiths. The ad suddenly ends, and the logo for Halo 3 is shown while the Halo Theme is played in the background.

The Kids
The kids, the clumps of grass around them, were real. The CGI doesn’t begin until you see the Chief’s helmet for the first time. . As for who the kids seen at the beginning are, Bungie has yet to give a straight answer. They may or may not be John and another female Spartan. KP has confirmed that the trailer took place on Earth:
 * Konrad - Frankie, WHERE does the trailer take place?
 * KP - The trailer takes place on earth.

However, he could have been talking about the second half of the commerical where John wakes up from his dream in a battle on Earth.

At the end of the scene with the children the Master Chief's helmet is where the girl was laying down, indicating that the boy is looking at the helmet. It is also speculated that the girl is Kelly, one of John's friends. This implies that the boy in the ad is a young John-117 and John is having a flashback to one of his memories during his training on Reach (Something backed up by the non-Earth night sky).

Transcript
(Two kids are laying in the grass, looking up at the stars.)

Boy: "You ever wonder what's up there?"

Girl: "Like what?"

Boy: "Maybe someone up there is wondering what it's like here."

Girl: "I guess. Do you think we'll ever meet them?"

Boy: "I hope so. Don't you?" (He turns to look at the girl, but instead sees a MJOLNIR helmet.)

(A Wraith mortar detonates nearby. The lighting changes and Master Chief wakes up. Myriad voices are heard, some in his head, others from his radio.)

Girl: "Do you think we'll ever meet them?"

(He puts on his helmet, and regains his balance.)

Girl (faintly) : "Time to go"

Cortana: "Chief, leave me!" (not confirmed)

Soldier #1 (radio): "Is anyone out there?"

Soldier #2 (radio): "Chief!"

Soldier #3 (radio): "Marines! Fall back now!"

Sergeant Johnson (radio): "Any sign of the Chief?"

Soldier #4 (radio): "Negative, Sarge. I think we lost him."

Master Chief: (looking up at incoming mortars, pulls out shield grenade) "Not yet."

(He throws a bubble shield onto the ground, creating a shield that protects him from the blast. After the dust clears, he holsters the pistol and grabs the assault rifle on his back and runs forward. He leaps off a cliff into a pack of brutes, and the ad ends.)

Bungie Official: "Rated M For Mature"

Video Trivia

 * One of the voices the Master Chief hears while regaining his balance (Soldier #2 above) sounds like Sgt. Johnson, meaning perhaps that it is another voice in his head, like Cortana's or the girl's.
 * The pistol Master Chief was wielding was an early look at the M6G.
 * When Master Chief grabs the MA5C Assault rifle, the "On" button and Marathon logo are clearly visible.
 * One of the brutes is using a Gravity Hammer
 * A few of the brutes are using Spikers.
 * Master Chief jumps into a crowd of Brutes and New Wraiths in last seconds of the ad
 * When the Chief activates the shield grenade, you can clearly see the Mongoose in front of the chief right before the mortar round makes contact.
 * Just before Master Chief leaps off the cliff, if you look at the sky, the clouds seem to be in a circle and there is a flash of what could be lightning. This is similar to the Halo 3 Annoucement Trailer where just above what might be the Ark, the clouds are spinning in a circle and there appears to be lightning in them. That may mean that the battle part of the trailer is near the remains of Old Mombasa.
 * On the MJOLNIR Helmet, shortly before Master Chief reaches down to grab it, a small image appears. Speculation implies that it is Master Chiefs head, though it also looks, somewhat, like a dog's head. This may coincide with an inside joke within Bungie, regarding a dog's head which they need to take over the world.Others say the face looks like a pig, or a dog. This was later confirmed to be clouds and Covenant cruisers.