This took longer than I thought. My motivation starts to fail me, but I have to finish at least the most widespread species.

The Ikassi (singular: Ikassa) were the first race to take the steps into space. Their history sounds kind of boring for human ears, because there were almost no wars or even aggressive conflicts, as the Ikassi are propably the most peaceful species you'll ever meet. That's probably the reason why they had the capacity to start civilization and research early, but also the reason why they were never in hurry to leave their planet. But in the end they still won the "race" and explored the stars, as they faced the only problem you could solve with conflicts: overpopulation.
The Ikassi do live in some sort of communism, and it works for them pretty well. Family and friends are the biggest assets, and as long as everyone has a shelter and something to eat they're happy. In fact most of the other races are kind of irritated by their everlasting cheeriness, as they won't. stop. being. so. freaking. positive. All the time.
But the first encounters and the start of the galactic community taught them that not every species lives in harmony and peace. The Ikassi learned their lessons early enough after their first hostile encounters with InsectoidSpeciesIHaveToIntroduce and started to rearm themselves. They had the resources after all because of their head-start in the galaxy, and they didn't stop the military build-up until they had the biggest fleet of them all, true to the motto "If you want peace, prepare for war". They never really had to use their fleet in whole, and nobody wants to find out if the Ikassi really know how to use all this firepower.
Right now they are the balancing factor in the galactic politics and try to negotiate between the species in terms of territory, trading and general politics.
Fun fact: Ikassi don't run but instead jump like jumping mice or kangaroos. Imagine them jumping between the bigger races, in a hurry, with a smile and a shitload of bags on them. Aww.

tl:dr: Ascar grew tired of always grumpy humans, thought about how everything would be if there would be no aggression, and put these thoughts in little mice.