Like Leona Lewis, Janet Jackson is a musician first and foremost. Unlike Lewis, Jackson has shown an active interest in acting, and has a number of television and film roles to her name. You'd have thought that would mean that she was open to the idea of kissing people while in character, but apparently not. She did eventually agree to kiss Tupac Shakur while filming 'Poetic Justice,' but it took a lot of persuasion.
Although Shakur and Jackson sizzled on screen together, it sounds like Shakur found her hard to work with. She's heard rumors that Shakur was something of a 'player,' and so tried to insist that he was tested for AIDS before kissing her - which suggests Jackson's understanding of how the illness is transmitted could use some work! A deeply offended Shakur refused. Jackson eventually kissed him anyway. We doubt they spoke much afterward.