This rather short-lived series which aired on ABC in 1975 was produced by Sid and Marty Krofft. It is about the misadventures of two androids (named Fi and Fum) as they attempt to return a young boy named Jerry and his babysitter Alice back to present-day Earth.
The episode "The Tiny Years" has them travel to the year 2465 where all the inhabitants are shrunken and thus distrust anyone who is bigger than them. Jerry wanders off only to get tied down by some shrunken people called the Littlenicks in order to warn the "Biggies" to stay away from them. He later gets rescued by Fi and Fum's pet "Dorse" (a weird dog-horse hybrid).
I found this episode on one of those "Saturday morning cartoon compilations" on Youtube. It is best if you watch the entire episode just for taking screenshots since there are commercial breaks.
Found a much better source on Archive.org to replace the YouTube video on that Library link. I said earlier that you should take screenshots after watching the episode in order avoid watching the commercial breaks in that other video.