During the scene at the airport where Michael talks to the camera for the last time, he takes off his mic and says "This is gonna feel so good getting this thing off my chest". Afterwards, the audio cuts out and if you look and listen very closely Michael says to the cameraman "That's what she said".
The bald guy seen leaving the elevator as Michael is getting on was in season 3's "A Benihana Christmas". He was part of the couple on a date that was sitting at the same table as Michael, Andy, Jim and Dwight at Benihana.
The scene where we see Michael through the shades of his office window placing his trophy onto his desk and then straightening it out, mimics the clip from the opening credits where he does the exact same thing, used since season 1. It's one of the few clips that have stayed in the opening credits throughout the years of changes.