Things Heating Up Between Rihanna, Chris Brown?

Evidence keeps mounting that Rihanna and Chris Brown are back together, despite the fact that he insists they're just the "best of friends." Just last night, Rihanna tweeted a picture of a shirtless Chris Brown laying in bed, boxers on full display, TMZ reports. And they spent Thanksgiving together, photographed partying and then leaving a Berlin nightclub together, E! reports. En route to Germany, Rihanna tweeted, "All alone in my big ole jet!!! See u soon lover." And of course, they recently collaborated on yet another song pointedly titled, "Nobodies Business." (More Rihanna stories.)