Great topic! I really wish that there were more stuff out there that played with this idea of the girl who isn't really there to participate or star but then decides to participate just a little bit by non-chalantly blowing a guy or something.
Upthread, someone posted this video with Amy Brooke as the "assistant" in a gangbang with Jayla Starr. I'm not into the race angle, but Amy's role in the video is pretty hot:
http://www (dot) xvideos (dot) com/video1035029/jayla_starr_4
(the action starts about 2:00)
There's also this orgy where Gwen Diamond is kind of an onlooker and sucks a few dicks briefly, but only gets fucked for a second before the cameraman tells her to get out. She actually apologizes for getting carried away!
Full video is here:
http://www (dot) xyou (dot) com/it/s2/episode/7610/
(the part I'm talking about is around 20:10)