The plot centers on Jess's boyfriend Sam and his old flame, Diane. Jess talks through her feelings about Diane's reappearance with Cece at the neighborhood bar where she works. Sam and Diane, of course, were an iconic on-again-off-again couple at another TV show's neighborhood bar, Cheers.
Diane is wearing a trench coat similar to the one Nick did the first time he kissed Jess.
Schmidt is wearing a part of the swuit from season 4.
Diane (Caitlyn Fitzgerald) and Sam (David Walton) were both in Masters of Sex where David portrayed Caitlyn's love interest.