Goblins

Goblins are most likely the default enemy NPC. They seem to be the easiest to kill as well as some of the smallest. In the E3 demo, you can see some Goblins in what seem like airships.

Combat
Goblins seem relatively easy to kill (3 hits with the default "brawler" and "shooter" setup - E3 presentation), and while this remains to be seen, their appearance so far shows them being small and weak.

Brain
Like everything else in Project Spark, you can edit the goblin's brains, but on default goblins are hostile and aggressive (attack without being attacked).