Season 5, episode 36, aited June 19, 1964.
Two children escape their bickering parents through a portal in the bottom of their swimming pool to a magical land watched over by a kindly old woman the children call Aunt T. The episode was one of the first shows on television to really address the problem of divorce and bad parenting, and in part it represents wish fulfillment or escapism for children in such situations.
Numerous production problems delayed the premiere of this episode, which was originally scheduled for March 20, 1964. Most noticeably, back-lot noise rendered much of the outdoor dialogue unusable and the entire cast (except Aunt T) consequently re-dubbed their outdoor dialogue in September 1963, but Mary Badham's (Sport) voice was still deemed not right. Eventually, voice actress June Foray, best known as the voice of Rocky the Flying Squirrel in the Bullwinkle cartoons, dubbed Sport Sharewood's lines for all the scenes that take place outdoors (and sounding very much like Rocky). In the finished episode, the change in Sport's voice is noticeable when she moves indoors.
*****The cache you seek is a micro*****