First of, this was done on the PS3 and I don't know if it works on the Xbox360.
Private Match Game File [ Just any game file that's for private match, e.g. = hyper speed & hacks or something ]
1.First go to Multiplayer then just select Player Lobby. [Just like if you would play online]
2.Now make sure you have both controllers ON.
3.It will say "Press X to Play" So join with your 2nd controller.
4.Now load your private match game file! [ Playercard> Files > Game File[Must be private match I think]]
5.Now it will take you to a private match, now you will see your 2 players as usual, but also it says "Press X to Play" Also it will show a "2" in-front of the "Press X to Play"[ Even tho there's already a "2" ]
6.So Right now you just tricked it to think that player 2 hasn't joined yet.
7.Now start the match...You now will only see 1 screen instead of split screen, even tho player 2 was in the lobby... You must select a team and run around like for 15 seconds, then end the match!
8.Now you will see NO Usernames, Only 1 spot that says : "Press X to Play"
You now press X Using your 2nd controller, Now you can invite your friends and they wont see you!
Mics don't work when you're invisible. D:
Warning! Do No start the game when your invisible, it will take you back and give you an error!
Also If you start it with your friend there, it will freeze on the loading screen [ awaiting challenges <--- screen][Doesn't always happen!]
If you change the lobby to a player match, It will only show [player 1] And If you invite someone now, they will overlap into your username. So it looks like you are them.
Also You can change lobbies to combat training!
Also the player 2 is in the lobby when you start the game, even tho its not split screen.
When you try it in combat training with 9 enemies, There will only be 8 enemies due to player 2... even tho player 2 is not visible or active.
Hopefully you fine this glitch useful, BTW I Found this glitch by accident!