In the episode "A League of Their Own", Cliff meets Marc St. James in a photoshoot Wilhelmina has him supervise, and invites him to watch the film Psycho with him. Marc later cancels their "date" to go out with an underwear model, as Marc hadn't realized Cliff was interested in him. Offended, Cliff tells Marc he was disappointed as Cliff thought there was more to Marc. Near the end of the episode, however, they end up spending their night watching Psycho.
In "Something Wicked This Way Comes", Cliff suspects Marc doesn't want to be seen with him when he comes to visit Marc at work, which is confirmed when Marc introduces Cliff to Amanda as a "friend". He breaks up with Marc, stating he "has too much respect for himself to put up with this". When Marc learns he will get a "plus 1" invitation to the Slater-Meade wedding, he calls Cliff to patch things up.
In the seventh episode of Season 2, "A Nice Day for a Posh Wedding", Cliff and Marc are back together. Marc panics over how Cliff dress at the wedding, but is very pleased when Cliff appears clean shaven in a stylish suit. Cliff is later seen talking to a model he used to work with, igniting Marc's jealousy and causing Marc to break up with Cliff. They got back together moments later and sit together during the entire wedding.
Marc and Cliff, while going to rent movies, discover Wilhelmina's first choice for a surrogate mother, her manicurist named Brandy, was actually a Dominatrix/porn star. They alert Wilhelmina, thus averting disaster.
In the third season, Cliff returns in the sixth episode "Ugly Berry". After he is maliciously cut from a photoshoot by Kimmie Keegan, he appears very briefly, lying on Betty's sofa and distressedly eating a slice of pizza while while Marc, Betty, and Amanda plot to get Kimmie fired.
Cliff asks Marc to move in with him, an act of commitment overwhelming Marc and causes him to start avoiding Cliff. In Marc's panic, he hooks up with Betty's neighbor at the MODE afterparty she holds on top of her apartment building. Cliff later shows up to withdraw his offer and show his understanding for Marc's reluctance, but Marc impulsively asks if Cliff wants to get married. Cliff excitedly agrees. In the following episodes, Marc avoids all mention of the pending nuptials, despite prodding from Amanda. On a work-related road trip with Marc and Betty, Amanda finds a receipt for two wedding bands in Cliff's car, which causes Marc to hyperventilate. On the same trip, Marc accidentally crashes Cliff's car (which he was borrowing), and dramatically bemoans Cliff will never trust him again, a claim the ladies dismiss. Later on, after coaxing from Betty, Marc confesses he cheated on Cliff and Betty encourages him to tell Cliff the truth. Mark asks Cliff to meet him at work, and at first confesses he crashed the car, a revelation relieving a nervous Cliff. However, Marc admits his infidelity, and a stunned Cliff leaves in tears. In the following episode, Amanda mentions Marc is no longer engaged.