Finished the second season tonight after stretching it out to savor it. Really enjoyed it, though not quite as much as the first season. I think that's mainly because the kids spent so much of the season locked up in the pump house, and because our core trio (Big Man/Tommy Jepperd, Sweet Tooth/Gus, Bear/Becky Walker) spent most of the season apart on separate journeys. But the payoff in the last third of season was really effective.
Going right into the second season after rewatching the first season on Blu-ray, I was surprised at how seamless it was. The only way I could tell that there was over a year between shooting season one and season two is because the girl who plays Wendy went from being half a foot shorter than Gus to a couple inches taller than him between 1x08 and 2x01.
Apparently they filmed the third and final season back to back with the second season, which was smart given that a number of these kids look like they're on the verge of puberty.
A couple interesting facts about the hybrids: Bobby is not (primarily) a CG creation. He's an animatronic puppet, with 2-3 puppeteers controlling his body, and another three puppeteers controlling his face and mouth. The visual effects were mainly used to erase the puppeteers from shots:
Also the girl who played Maya (the monkey girl), is Amie Donald. She was the girl under the mask in M3GAN. I can see it, because both characters require a lot of unorthodox movement and her dance background would be a real asset for that.
It also definitely feels like this was designed to be a three-act story. The first season definitely felt like a beginning, this season feels like a middle, and the second season finale definitely feels like it's laying the groundwork for the end.