Artoo and Threepio were never saddled with smoldering romantic subplots, so it makes sense that they’d schedule their RAM jams off-screen. And indeed, the 1975-1979 Italian adult comic book Cappuccetto Rotto boasted this cover showing the droid duo in the midst of group amore. Lest we not forget, C-3PO is used to this kind of shameless exhibitionism.
http://io9.com/5910424/the-curious-case-of-the-vulgar-c+3po-trading-card
We added the concealing stars to the Orgie Stellari above, but you can find a full, not safe for work gallery of Cappuccetto Rotto covers at this link. There you will discover such characters as girl-on-girl Batman (left) and a priceless Manticore photo-bomb (also above, just because it cracks me up). I adore the Manticore’s complete inability to play it cool.