A good example of how you can make a title seem, in retrospect, like complete gibberish: presumably, this episode is named after the 1990 film Arachnophobia. But sticking "ducky" in the title in place of "rachno" completely severs the relationship to spiders, leaving anyone not up on their middling horror movies completely in the dark. "Aducky?" So it's the fear of…an absence of ducks? Wuh? Well, I guess we're all probably experiencing that to an extent as we wait for a new Disney publisher to emerge.
I'd kinda forgotten about Moliarty. Well, not literally; I may at some point have vaguely thought, huh--I wonder if that mole guy's ever gonna make a reappearance. But his initial appearance didn't make much of an impression, and honestly, I didn't really remember what he was like. Well, now he's back. Hurray? Sure; why not. Though here, at least, he's really nothing more than a generic dick who wants to destroy surface life just 'cause of some kind of molecentrism. He's messing around with radiation 'cause he's after a rare mineral called "canardium" to power his evil machine, and a spider gets mutated and grows to be giant. I thought it also mutated to have a human face, but as we later learn, all spiders of that species are like that. Weird. Anyway, he's really childlike and sweet but also quite dumb and easily manipulated, so Moliarty enlists his aid. When he bites DW (for which he is immediately contrite), the latter grows two extra pairs of arms and decides that his new superhero identity will be "Arachnoduck."
And that's about that. Moliarty, like, loses and stuff. And that's about it, really. Nothing too spectacular, although I really do like the giant spider. If they had wanted Moliarty to feature more prominently in the show, they really should've done more to make his character distinctive.