when an old boyfriend humiliates her, barney comforts her, and they have sex. this initially causes friction between her and ted, but he ultimately accepts it. barney and robin have what they believe is a no-strings-attached sexual relationship for a few months, but they become an official couple after some aggressive prodding from lily. they soon realize that they don't work as a couple, however, and break up. they remain friends, but it is implied robin never truly lets barney go. despite spending most of "challenge accepted" plotting with barney to find a way to prevent ted from pursuing a meaningless relationship and rekindling her relationship with him in the process, she also pressures barney into approaching nora (nazanin boniadi), a woman he likes. however, when barney asks nora for a cup of coffee, robin realizes she may still have feelings for him.