This is kind of a fun one, but it starts to feel long toward the end. It seems like it's going to be a lesson in how quiet, calm, self-assuredness is preferable to chest-thumping bravado, but the spirit of competition gets the better of everyone. The idea of being secure enough in your own masculinity to walk away from a fight is something you'd NEVER see in the hyper-testosterone-driven tv shows of today.
In much the same way, I find it funny how the episode takes token offense at the condescending attitude the aliens' have toward women when most LIS scripts don't have any higher a regard for them.
The cave monster here rates down there with the most uninspired the series ever offered up.
I echo the sentiment of the previous poster re Dr. Smith and the Robut; the show was really onto something here, developing them as perfect foils for each other.
***** SPOILER ALERT *****
The thing I appreciate the most about this episode is the ambiguity of the final fate of the alien father and son as they challenge the cave monster one last time.