The parts with Joey on "Pyramid" were shot on the "Pyramid" set. The "Pyramid" audience got a big surprise when they thought they were there to watch a real game of "Pyramid" but instead got to watch the taping for a "Friends" episode.
There are several points during the episode when Lisa Kudrow can be seen trying not to laugh at Danny DeVito's performance.
Ross makes mention of a number of different people that he would like to see while at the reunion, one of them being Michael Skloff and another being Jeffrey Klarik. Michael Skloff is the co-writer of the iconic Friends (1994) theme song as well as additional music for the run of the entire series. Michael's wife, Marta Kauffman, was a co-creator of the series as well as a co-writer of the aforementioned theme song. Jeffrey Klarik is the lifetime partner of co-creator David Crane.
Danny DeVito's character refers to himself as a "50-year-old stripper". In fact, he was 59 years old at the time this was filmed.
In one scene Rachel is supposed to say that she will pay the stripper. In one outtake though Jennifer Aniston flubs her line and instead of saying she'll grab her check book she says she'll grab her paycheck. Danny De Vito who played the stripper joked and said he had witnesses and then said "Rhea, we're going to Tahiti." Referring to his wife Rhea Perlman.