Where does HarmlessVillain overlap with NoAntagonist?

If a character is said In-Universe to be a villain, albeit a Harmless Villain (and maybe not even very evil, more of an Anti-Villain; aren't some Harmless Villains also an Anti-Villain, since an Anti-Villain is ambiguously evil rather than a Complete Monster, if I'm right), but doesn't actually do anything remotely villainous (unless you count Poke the Poodle acts and annoying people, but not Big Bad-type schemes such as world domination or murder), and is just seen as an eccentric character, where's the overlap with No Antagonist?

The reason I ask is - having seen this on the Fif I And The Flowertots page when reading about British series.) If a character only does something that antagonizes the protagonist (Harmless Villain stuff, not Death Trap etc.) only once in a series (for one episode) and no other episode in a show that otherwise has No Antagonist would the series still qualify as having No Antagonist, and would that one-off episode also qualify as Something Completely Different?

I'm just checking before I make any major edits to work pages to avoid an Edit War and ensure I have the correct meaning of tropes.

edited 4th Jun '17 4:45:54 AM by Merseyuser1

Without more context, I'm not sure I see anything dramatically different enough that would qualify as Something Completely Different.

If there's just one episode with an antagonist, even an ineffectual and harmless one, the series as a whole would probably qualify as No Antagonist, but not that one episode.

Whether a character is a Anti-Villain or a Harmless Villain doesn't really say whether it's an antagonist, though. A villain is usually an antagonist, but there's also Villain Protagonist. However, how effective or harmless they are doesn't their role in the plot. It's probably possible to write a story where a perfectly plain potted plant is the main antagonist.