It's not gnomes; it's the blue dudes from the Twilight Zone TV remake!
Oooo! I love that episode. NOBODY knows what I'm talking about when I mention it.
That episode always stuck with me. As did the one where the two boys are in their scientist father's workshop, trying to figure out why he was missing, and they keep finding progressively larger (abnormally larger, that is) animals, and you realize in the end that an enormous (Jilli font) spider was the likely culprit. Gack. Spiders don't really bother me, unless they're the size of a car.
(...is this the episode where the guy was followed everywhere by these tiny fellas that NOBODY ELSE COULD SEE? Because I saw that one, whether it's the one you mean or not, years ago, and it creeped me THE FUCK out. Stayed in my head ever since. But I don't remember if they were blue.)
Fay, it's this episode: [link] which delights me even more in retrospect that one of the writers was Rockne O'Bannon (of Farscape), along with Harlan Ellison, who isn't too shabby, either.