Kimora Lee Simmons and Djimon Hounsou aways struck us as a rather puzzling couple - he appears to be a serious and dedicated actor and she seems rather - well - frivolous. Our friend Nelson Aspen was working out at a posh Century City gym when the aforementioned couple walked in. Djimon wore a simple black workout jacket and baggy pants and Kimora was uncharacteristically low key - also in black with a ponytail and no makeup. Our witness said that they were very comfortable together - smiling and joking. They both did cardio and weights with great vigor - sometimes separately, sometimes together. "They were playful and sweet to each other." Kimora is motivated to work out because she was accused of being pregnant recently - and she isn't.