The Keeper is an alien who travels the galaxy collecting living pairs of interesting or rare animals. His courtly overtures towards the Robinsons belie his true intention -- to add a pair of humans to his incredible menagerie.
The Keeper, a collector of animal specimens, comes to the planet to collect two of every kind. The Robinson party only becomes aware of his presence after Dr. Smith is ultra-sonically mesmerized into entering one of his cages. The Keeper, who can be as charming as he is condescendingly arrogant, eventually comes to see the Robinsons and thereafter sets out to add a couple of them to his collection.—statmanjeff