When Nick leaves the lab, he looks at the case board and remembers many moments in his career, including one from the first episode where Warrick puts a "solved" placard on his 99th case. Nearby is shown Nick's column, who also has 99 cases solved. Back in the present, Nick puts a "solved" placard on his name, but the board shows the same cases he had in the first episode, as if he still hadn't solved his 100th case. Apparently it's the same board with some names changed.
Sara Sidle asks if Nick is still on for drinks at the bar, but her character has been sober for years as she is an alcoholic. This was missed by the new show runner.