May the best robot win!
Here, the stranded Robinsons unexpectedly discover a quiescent "robotoid" in an overgrown grove near their homestead, covered in vines.
Robotoids have a "choice,” according to the Robot in the way they follow (or don't follow...) orders and instructions.
Dr. Smith derides the familiar family robot as a "clumsy has-been" and "obsolete" as, in short order, Robby the Robotoid becomes practically invaluable to the marooned Robinsons (save for Penny, who has mysteriously vanished from the entire episode...without it being noticed by her Mom or Dad).
In the end, it's a battle-to-the-death between a nearly-invincible Robby, the most famous robot in film history, and a vastly-under-powered Bubble-Headed Booby, the most famous mechanical man of television...
Let's face it: haven't we all felt displaced like that from time to time? By a brother or a sister? By your best friend's 'new' buddy?