The good, the bad, and the almost irrelevant. They are the miscellaneous characters that are there to answer that one question, explain away that one plot hole, assist in adding development to that actually relevant character, or give that good (or bad) advice. We usually never learn their names. They are there and they are gone as soon as they serve their purpose often never to be seen again. They may not be the most memorable but definitely have a role to play.
After you get out of your captain exams you are confronted by a Celd. He criticizes your actions and later gets into a fight with you and your siblings. He was confirmed as part of the Celd alien race in Chapter 1.
He was a bartender at the space station. He serves you a Galaxy Blaster sent by Titania. In Chapter 4, his name was revealed to be Corvus and he was confirmed to be part of the Epoch alien race. Eos recommends him to work at the Atlas. You can encourage him and Argo to pursue a romantic relationship.
Rana's unnamed boyfriend is a member of the band, Righteous Rectitude. He and his band are raising awareness for the the Jura's plight. They have not yet released their first album, but when they do he and Rana plan to run away together and join the Jura's war effort.
Holmes bets all your money on a race, backing a Kraken. For the majority of the race, the Kraken just sits at the start line blowing bubbles until the race is almost over and he flings himself across the finish line before everyone else.