Leonard is portrayed as a moral, honest person. He has a quest to kill John G, because he believes it will provide justice for his wife's rape and murder. He refuses to kill Dodd for Natalie, because he won't kill for money. He wanted to get ahead in his insurance company, but he also wanted to be honest with Sammy's wife and tell her that Sammy was physically capable of forming new memories, but psychologically unable. So, why does Leonard steal Jimmy's designer suit and then steal Jimmy's Jaguar? He takes the suit when he still believes Jimmy is John G and perhaps it's part of the "make him beg" humiliation, but he IMMEDIATELY begins wearing the clothes - WHY? And taking the car is after Leonard apparently rejects Teddy's explanation of what happened with John G, but gives no reason for stealing the car.