Alan Hale Jr. plays the owner/chef of the restaurant Chief O'Hara goes to for lunch. The character's name is 'Gilligan.' Hale is best known as The Skipper from Gilligan's Island (1964) with first mate named Gilligan (played by Bob Denver).
This was Anne Baxter's first appearance as Olga. She previously appeared as the female magician Zelda the Great in the first season.
Along with How to Hatch a Dinosaur (1967), this episode was originally intended to air as part of a three episode sequence. Producers changed their minds, and the third episode featuring Egghead and Olga, The Ogg Couple (1967) would later air as a stand alone episode.
The region of Bessarabia actually exists in Eastern Europe. It is part of present day Moldova and the Ukraine. It's likely the basis of the name of Olga's realm.