The scene where Oscar sees the hard wood beneath the carpet and says, "I always knew it was down here. I just never dreamed that I would actually see it." is in reference to Season 7: "Dwight Schrute: Acting Manager" when Dwight's gun discharges and a bullet goes through the carpet (and the hard wood). Oscar notices the hard wood for the first time.
When Pam is in the car with Darryl, she refers to Jim as "Gumby with hair". This is a callback to S5E13 "Stress Relief". When Michael is giving his roast of everyone in the office, his roast of Jim is "Jim, you're 6'11" and you weigh 90 pounds. Gumby has a better body than you."
While Clark is trying on the suit, Dwight claims that there is no "Boring Island."
Just north of Samar Island in the Philippines, is Boring Island.
Just north of Samar Island in the Philippines, is Boring Island.
Hollywood Suit Outlet on Hollywood Boulevard stands in for "Stone and Son's"
When Dwight and Clark are pretending to be father and son, Dwight is imitating Oliver Twist in the 1968-musical 'Oliver!', asking for some more gruel in the poorhouse, holding his bowl: "Please sir, I want some more"