Hannibal Day threatens his organist by saying she can be replaced by records from Gaylord Carter. Carter was a famed organist who started in silent movies and moved to radio in the 1940s and 1950s.
Scrawlings in the Tomb of Kanin Ra include "Kharis Call your mummy", "King Tut Sphinx 54-1000", and "call after 8 P.M. 460 B.C."
Victor Buono appears after Max visits the National Museum in Cairo, Egypt. "King Tut Sphinx 54-1000" is among the scrawlings in the Tomb of Kanin Ra. Buono had previously played King Tut in Batman (1966).
In Max's phone booth/coffin, the topmost graffito, scrawled in white, is KHARIS CALL YOUR MUMMY, seen around 01:35 and following. Kharis is the name of the mummy in several Universal sequels to The Mummy (1932).
Hannibal, around 18:14, introduces 99 as "Helen Trent" instead of as Helen Blake. The Romance of Helen Trent, unlike the one in the episode, was a real-life radio soap opera, the longest-running one ever; it debuted in 1933.