Dwight mentions that Creed was a member of the band "The Grassroots" in the 1960's. The actor who plays Creed, Creed Bratton, was in fact a member of this band in the 1960's.
A few of the cast watch Ed Helms (Andy Bernard) give a speech at Cornell on YouTube. In 2014 Helms actually gave a Convocation speech at Cornell University which can be seen on Youtube
The woman in the panel audience who says if she had Jim "he could do anything" is The Office writer Allison Silverman.
In the original script, Jim was supposed to prank Dwight one last time with an extravagant Matrix scheme; this was cut out most likely because they were short for time. The scene was later released on Peacock as well as The Office YouTube channel.
The panel audience member who asks Pam how she could doubt Jim is Jennie Tan who runs the fan site officetally.com She asked the producers if she could be in the finale and they said yes.