Spoiler: A Scanner Darkly

So, I thought that it was clear almost immediately that Donna was the boss.  I think that they even flashed her face when they did a close up of her scramble suit (!).  Also, the height difference and body type were a total give away.  I can’t remember exactly, but I think there’s even a cut that goes from the two out of their suits to a shot of them in their suits — so you can detect the similar proportions.

Maybe it’s just because they really used the same actors for both scenes and it was a give away.