Penny and Smith discover an odd mirror that acts as a doorway to a strange 'Neverland' where the younger of the Robinson sisters is granted her ill-considered wish not to grow old (and not to get all 'girly' like big sis Judy). The premise, that the 'other-sides' of all mirrors are connected in some vast dimension is intriguing (a similar premise was at the core of Heinlein's 'The Unpleasant Profession of Jonathan Hoag') but the episode does little with it beyond setting up a 'Penny matures' story. Michael Pollard plays the odd 'Peter Pan'-like' mirror-dimension dweller - an interesting character who forever seems to battling an improbable hairy monocular beast and does not cast a reflection of his own (which I found a most interesting revelation, sadly not followed-up on). Irwin Allen's famed frugalness is on display as the mirror-land is full of plastic sheets and props from a variety of movies but the overall effect is nicely other-worldly and surreal. Too bad more wasn't done with the story, especially as to the origins and destiny of the time-less boy. In recent watchings of this venerable series I have found it odd (and slightly off-putting) how child-like and fragile Penny is portrayed when compared to her competent and resourceful younger brother Will. This was one of the first episodes to punctuate Dr. Smith's antics with typical comic 'musical cues' (a sign of things to come).