Mass Effect 2 - Hidden Dialogue (Tali and Legion in Archangel Mission)

Through editing the save games you can actually add whichever characters you want at any time in the game (only after you meet the Illusive Man though due to an apparent bug if you do it during the Lazarus Research Facility mission). More strangely is that they have dialogue for these missions. It's impossible in every way to have either Tali or Legion at this point in the game. Either Bioware made them record lines in case people would do this kind of editing or you were originally going to be able to have them at this point in the game