As much as it would be cool to destroy him and believe me I have tried alot but sad to say no you can’t. I mean seriously what are we both thinking bungie obviously only want you to kill him at the END! I mean come on bungie why can’t we kill him if we know we are pretty much screwed! I once heard him say this:

“Ow that hurt my feelings. Oh my god I have feelings? I’m a real boy!!”

Second of all, when Chief sees the hologram of Cortana in the last cutscene, the Arbiter doesn’t — Thel asks, “What do you see?” If Mendicant Bias was projecting a hologram, the Arbiter would have been able to see it. It was probably just Cortana hacking his armor and projecting an image of herself over what he was seeing — the armor’s linked into his brain, so she could have easily altered his sight, making a change that the Arbiter would not have been able to see.

That’s because they ARE 2 different species. It’s pretty clearly stated in the terminals. Part of the terminals story is how the Forunners find the humans…the only possibility this leaves for them being the same species is if the forerunner were humans who left earth for so long they forgot where it was and then found it and discovered thier long lost siblings. Possible, but not as likely. Truth just makes the mistake of assuming since the humans are reclaimers that they must be the surviving Forerunners as opposed to being the species the Forerunners decided to allow to reclaim (hence the name) thier technology (or perhaps just reclaim the galaxy from the Flood).

The other fun stuff comes after you’ve destroyed the Scarabs and other enemies outside the citadel. I’ve been told many times that the IWHBYD skull is needed to get en Elite to ask, “Is this because of Reach?” after getting shot, but if you take a Hornet and strafe one of the two Elites in the green Phantom the Arbiter waits under at the light bridge, one of the gunners will eventually say it. Similarly amusing are Brute’s fire bombs’ efects on the same two Elites. When the fire is thrown to the portion of the Phantom above him, I’ve heard him scream, “Ah! Fire!” in fear. When he and/or the platform below him are set ablaze, though, he screams in agony for a moment before shouting, “Ah! I’m burning!” When he once died and fell out of the Phantom onto the light bridge below (after which I used a few melees to throw him off the bridge), Spark said, “Pity,” though I don’t know if it was a direct result of my killing the Elite. ‘Twas a joyous moment!
If you’ve still got the tank or a Hornet, if you fire on the Pelican, still floating nearby, enough, it’ll eventually start to flit about wildly, probably attempting to evade your fire. The wierd part is that I’ve seen it dogde and weave its way into a rock face, so that the bulk of it’s body has diappeared into a wall. You can’t walk through the wall, but you can land one player on the Pelican in Co-op while the other harrasses it with a Hornet, creating a sort of mechanical bull game once the dodging and weaving begins.

Regarding the two jumps to get onto the Scarabs: be careful. I’ve taken Warthogs off those same jumps after the action had subsided and have, many times, died on impact as if I’ve fallen off a cliff, maybe five feet from landing. It’s pretty amusing, since the Chief flails and screams while already on the ground, but it’s also a frustrating setback.