I was thinking about the Helmacrons a couple of days ago. And, aside from the fact that I just can't picture how a teeny, toy-like space ship managed to travel through the galaxy, I wondered about how the Helmacrons came across the Yeerks. Did they visit the Yeerk planet one time? Did the Yeerks come across them some time in the thirty years that they were space-faring? I mean, the Yeerks couldn't have possibly thought that the Helmacrons could be infested. And, in their debut, Animorphs 24: the Suspicion, Visser Three is said to have mouthed the word "Helmacrons" while in human morph; so he (and possible the Yeerk race) was familiar with these pests...somehow.
I had a theory: that maybe the Helmacrons were somehow natives of the Yeerk home world--one of the mere hundred species of the Yeerk home world. But, then one must ask, how did the Helmacrons manage space travel? I doubt they stole an Andalite toy spaceship that happened to be able to escape the planet's atmosphere...Althou gh, it could explain why they use morphing energy to fly/shrink people...
Maybe they're from one of the moons orbiting the Yeerk home world? Again, there's still the issue of how they managed space travel?
The Helmacrons baffle me. Maybe it's just better to pretend they didn't exist.