There were a lot of big moments on last night's (March 22) "Once Upon A Time": Hook confessed his feelings for Emma; we discovered the location of this half-season's macguffin, The Author; and we finally learned Ursula's backstory.

But the biggest moment? When a Ghostbuster delivered the most ridiculous line in the history of the show and somehow made it work.

The set-up: In the fairybacks, we learn that Ursula has her mother's singing voice, in a riff on the Disney classic, "The Little Mermaid." She wants to travel, see the world and use her gift to bring song to the seven seas instead of crashing ships siren-stylez.

On the other end of the argument is her father, King Poseidon (Ernie Hudson), who wants Ursula to stay safe and not go where the people go, using those -- what do they call them? -- legs.

Naturally, Ursula leaves, meets Hook, has her voice stolen with a nautilus shell, and never forgives her Dad.

In the present, Ursula works with Hook to get her voice back, which has been trapped in the Jolly Roger -- which itself is trapped as a ship in a bottle after Ursula uses her magic tentacles to bring it to Storybrooke from the Enchanted Forest.

Related: distilling "Once Upon A Time" plots into one sentence is a joy perhaps greater than witnessing the birth of your first child. True story.

Back to the episode, they get the nautilus shell from the ship, but only King Poseidon can reverse the spell, so Ursula throws Hook overboard. He's rescued by the LM herself, Ariel, who spouts some nonsense about Elsa, Arendelle and some sort of intrigue I couldn't even remotely understand, and I've watched this show for the past 35 seasons. So that's saying something.

Returning to her cadre of villains, Ursula decides to give up, until Hook reveals a surprise: he's brought Poseidon to Storybrooke.

That's where the best phrase in the history of the show comes in. When asked how he got there by Ursula, Poseidon responds, with a totally straight face:

"A young mermaid brought me through a portal."

...And that explains the whole thing. Nobody asks any further or follow-up questions, because none are needed. A young mermaid brought the king of the seas through a portal so he could talk to his daughter, and that makes total sense to everyone.

That's "Once Upon A Time" in a nutshell, right? Why we watch the show? Because beyond the ships (both fan and literal) it's that something totally bananas can happen, and everyone just rolls with it.

Thanks to Ernie Hudson for being game enough to join the Fairy Tale Mystery Squad for a brief moment, and explicating this so well.

That said? Not having him hang out in Storybrooke and say, "I love this town!" was a HUGE missed opportunity.