So yesterday we had a thread about cut content, mainly dialogue from Mass Effect 2.
Through save game editing many conclusions can be made on how Bioware had originally planned the game. It's no major changes but still different.
The first thing is that Garrus was supposed to have been recruited later in game, probably around the same time as Samara and Thane. You can basically just swap him with Tali. Legion was also supposed to have been recruitable almost at the start of the game around the same time as Jack, Grunt and Mordin because he has full dialogue for these missions. If Garrus was supposed to be on Omega all along then perhaps Mordin was supposed to only have been attainable late in game as well.
Legion obviously ties in with that originally Shepard was supposed to be saved by Cerberus.
To give a few examples of all these "hidden dialogue" I'll link to a few videos I made.
YouTube - Mass Effect 2 - Hidden Dialogue (Tali and Legion in Archangel Mission) - Bringing Tali and Legion to recruit Garrus.
YouTube - Mass Effect 2 - Shepard and Legion rescuing Jack (Hidden Dialogue) - Only bringing Legion to rescue Jack (his dialogue is great).
YouTube - Mass Effect 2 - All Tali's Dialogue on Horizon - All of Tali's dialogue on Horizon. Shows that Thane has no dialogue at all recorded as Tali responds to herself at one point.
YouTube - Mass Effect 2 - Picking someone to stay behind with Garrus (including Hidden Dialogue) - All Garrus responses to leaving a team mate behind with him during his recruitment mission. Most of them are generic but a few are unique.
There are points in the game where a certain piece of dialogue can only be spoken by a specific character. A good example is whole Freedom's Hope. It can be set in stone that this was supposed to be the first playable mission all along as half of all dialogue vanishes if you dont bring Jacob and Miranda.