Ted meets a new girlfriend who turns out to be a leather cuff salesperson just slightly younger than 21 who convinced him to buy a leather cuff, so the gang is unable to meet her in person at MacLaren's. While he finds her really attractive, their age difference means he has trouble connecting with her. When he is about to end things with her,
Barney convinces him to give it a shot, which will allow Barney to live vicariously through Ted now that Barney is engaged to
Robin. Ted is about to end it with her upon realizing she has a really strong fetish for old people (Her believing him to be a senior citizen despite him only being in his 30s), but finally gives in when he realizes she likes
Star Wars. After they sleep together, however, Barney finds out that she is actually Carly, his half-sister, and is furious at this betrayal. Later, Barney attempts to marry Ted and Carly, and mentions that he finds the idea of a one-night stand "cheap, meaningless and disgusting". Both Ted and Barney then realize that Barney is done with his detox from one-night stands. Though happy with this freedom, Barney urges Ted and Carly not to sleep with each other again. While Barney struggles with his detox, Robin is going through her own struggles as well—she has difficulty getting used to being engaged. Where she used to get freebies by being a single, beautiful young woman, the ring now deprives her of them—including buying herself a beer at MacLaren's. However,
Marshall and
Lily assure her that when she looks at the man she loves, everyone else becomes invisible. Later that night, Robin understands the true power of her ring when she looks at Barney, and cleverly solves her problems by asking Barney to help buy her a drink instead. Meanwhile, Marshall takes to wearing Ted's leather cuff as it turns Lily on. This is in spite of the fact that his wrist starts swelling and eventually gives off a horrible smell. Lily finally explains that he does not need the leather cuff to turn her on. Afterwards, Lily receives a pair of elastic waist jeans in the mail by mistake, which turns out to be a big turn-on for Marshall. ==Music==