During Mass Effect 2, a character, Tali, will take her mask off, revealing her face. Sadly, however, her face is off screen, and so all the player gets is the hero, Commander Shepard, looking at her face. Members of the Mass Effect 2 forum have then photo-shopped what they think is behind the mask, such as Michael Jackson, Stephen Fry, and Commander Shepard himself. Hilarity ensues.

Reason
The thing with Tali’s face is because -- MINOR SPOILER WARNING -- in Mass Effect 1, it doesn’t matter how much you try, you cannot have a romance with Tali, nor she takes off her mask (because her race is used to sterilized enviroments (starships, yes, they live only in space). So, people who found her the most interesting girl to go with, was disappointed since Shepard seemed to see her as a daughter/kid.
However in ME2, Bioware gave the players a chance to romance her – and romance only happens before the 'final-misson' (can take a while), just like in ME1.
When the cutscene comes up, the face is off screen, and you’re left without any idea how Quarians and Tali look like..which gives mixed reactions of anger, disappointment, surprise and/or lulz, all depending on how involved you were with the game's universe.

The entire thread can be found here: http://social.bioware.com/forum/1/topic/105/index/931488/1