Starting just before the five-minute mark, in the first scene in Dave's office, his coffee mug alternates rapidly between shots from pink to yellow--with a total of seven color changes.
When Lisa and Beth are talking after the staff meeting where Lisa and Dave announce they've broken up, you can see the man Bill has relieved walk out of the booth and down the steps, straightening his tie. A couple second later when Lisa walks away and the shot pans out to Beth and Dave, the same guy is coming down the steps doing the same thing again, and the same sound effect of the booth door closing is used.
In the scene where Dave's mug goes from yellow to pink, Lisa tosses numerous multi-colored files on Dave's desk. These files go from spread-out to neatly stacked, back and forth. Also, the top file goes from red to blue, back and forth.
Before Dave leaves the love letter to Lisa outside the elevator, he mouths the words "Screw it." The audio is dubbed over with the words "Forget it" in their place.
After Matthew grabs Lisa and Dave's hands to try and settle things and they walk away dragging him across the meeting table, you can clearly see the corners of the inflated plastic cushion Matthew lands on (hiding behind the meeting table) to break his fall, as well as hear it, instead of hitting the floor.