This was the first script to enter the production phase. The episode's first Production Supervisor was called back to work on Jumanji (1996) and as a result, the episode languished for a bit. Egon was supposed to experience this mid life crisis right after the team formed in Darkness at Noon: Part 2 (1997).
One of the pictures Egon shows the pizza delivery guy features Tempus from Ghost Apocalyptic Future (1997).
Bobby, one of the security guards at the United Nations Headquarters, was previously seen being enslaved by one of the Runes of Kahlil in Casting the Runes (1997) and was working at the Bright Wave facility in Heart of Darkness (1997).
When they investigate the apartment where the three intellectuals were confronted with the Sphinx, the Ghostbusters visit the Shandor Building, the hub of the paranormal activity in Ghostbusters (1984).