(at around 53 mins) Jeff Goldblum is an extra in the crowd demonstrating in the scene outside of the legation. This can be seen on the on the PlayBack U.K. DVD.
This episode was first aired on October 12, 1975, exactly four months before the brutal murder of guest star Sal Mineo on February 12, 1976.
"Wit, Wisdom and Foibles of the Great Shriner": In the closing scene, immediately after Hassan Sarah's departure, the camera zooms in on a pensive Columbo and on this all-but-forgotten 1920s book. Very possibly it is part of the library assembled by the original owner of the house that stood in for the Suari Legation - Harold Lloyd.