|Planet of origin|
Varies during mating (no, really)
The Quarren were basically sentient squid-people with legs. They were evil bastards who had a beef with the Mon Calamari. Back in the days of the Jedi Civil War, it was rumored that there was only one Quarren in the galaxy, since they all looked the same and were only seen one at a time. The Jedi Exile proved this theory incorrect when she encountered multiple Quarren, even after witnessing—and causing—the deaths of at least two.
Behind the scenesEdit
The Quarren are almost always bad guys. The Mon Calamari are always good guys. Most Expanded Universe authors and George Lucas Himself made a universal agreement to keep it this way. Find a random Quarren character and a random Mon Cal character, and you'll see that the Quarren will always be an evil version of the Mon Cal.