In Season 4 Michael Benyaer took over for Brian George as Arjun Avasarala, Chrisjen Avasarala's husband.
When Avasarala is looking at her hand terminal and reading the announcement about the Cabinet Minister resigning from the UN, there is a small link under the headline saying, "Would you like to know more?" - a clear nod-and-wink to Starship Troopers (1997), where news items used this phrase repeatedly.
Hanging on the wall of the infirmary are four A-4 Oxygen Breathing Apparatus. These were used by the US Navy in firefighting and similar situations until 2001.