Brian (Paul Walker) and Dominic (Vin Diesel) have stayed pretty loyal to their original loves, Mia (Jordana Brewster) and Letty (Michelle Rodriguez), but the franchise's attitude toward the girlfriends has been more love and leave 'em. Mia wasn't in the second movie (2 Fast 2 Furious), but Brian had company in the form of Monica (Eva Mendes). In the fourth installment, Brian and Mia reunite, but Letty dies violently. But hold on: The fifth installment, this year's Fast Five, ends with a reveal that Letty survived. Guess someone besides Dom missed her. And Mia is with child, so in theory she should stick around for the next installment. But who knows? In a franchise that's all about speed, things can always change.