S3, E13: No one believes Charlie when he says that his relationship with Mia (recurring guest star Emmanuelle Vaugier) is getting serious, and everyone really thinks he's lying when he confesses that he and Mia have been dating for more than a month and haven't consummated the relationship. After a continuing series of chaste dates--walking on the beach, visiting an art gallery, going bowling--that end with Charlie frustrated at Mia's doorstep, he makes a proposal that threatens their burgeoning romance.