The (terrible) performance that Sophie acts out on stage during this episode is the very same (terrible) performance she did when the crew first met her in the series premiere.
In the premiere episode and the series finale, Parker changes clothes in an elevator with Hardison and Elliot.
During the heist Hardison says "20 pounds of crazy" to which Elliot responds "5 pound bag." This was the same sentiment Elliot shared during their first group heist in episode 1 when Parker jumped off the building.
Last show of the series.