By Sandra Gonzalez
Updated February 07, 2014 at 05:34 AM EST

Thursday night’s Big Bang Theory was positively loco(motive) but there’s no way to explain why without a little set up. So, here it goes:

In this Valentine’s Day-themed episode, what was supposed to be a romantic evening turned out to be a rough one for all three of the show’s major couples — Leonard/Penny, Sheldon/Amy, and Howard/Bernadette. At home, Leonard and Penny found themselves dealing with a Yorkie with a belly full of chocolate while Bernadette and Howard had to deal with a tense situation involving Sheldon and Amy.

You see, Amy planned a weekend getaway for her, Sheldon, Howard and Bernadette, and the way she convinced Sheldon to take part was by promising him a romantic dinner on a vintage locomotive. Once at dinner, however, Amy became upset when Sheldon befriended a fellow train enthusiast and paid more attention to his new (totally weird) friend than her. When she pulled him aside to give him a piece of her mind, a big fight erupted and Sheldon acted out — with unexpected consequences. Transcript and video below:

Sheldon: What is your problem?

Amy: It’s Valentine’s Day. We’re supposed to be having a romantic weekend.

Sheldon: Really? Because I remember you saying that this trip was going to be something we could both enjoy. Did you mean that or were you just trying to trick me?

Amy: Fine! It’s true. I deserve romance and I didn’t know how else to make it happen.

Sheldon: Well, if you want romance than let’s have romance! Oh, look, there’s wine!

[Sheldon drinks wine, grimaces]

Sheldon: Yum. Grape juice that burns. Now let’s look into each other’s eyes.

[Sheldon stares intensely at Amy]

Sheldon: You blinked, I win.

Amy: Sheldon…

Sheldon: What’s next? Oh, kissing’s romantic.

Amy, stunned: That was nice.

Sheldon: Good. [Pause] Um, the conductor said if I come back to the engine room, he’d show me how to bring the train through a crossing.

Amy: Okay…have fun.

Sheldon: Do you want to come with me?

Amy: Really?…I do.

Words are barely able to express how much I loved this scene. From the kiss on the lips, to Sheldon’s lean into the lip-lock. It was everything. Then to finish the wow moment with Sheldon’s invitation? Perfection. Honestly, to me, the more important moment here was when Sheldon invited Amy to share a special moment with him. Though, I’m sure if we were to ask Amy, she’d have a different opinion on the highlight here. Classic Flaky.

Other notes worth mentioning:

+ Raj’s Yorkie, the one that ate all the chocolate, turned out to be fine. And Raj, other than being wildly mad at his dogsitters Penny and Leonard, was better than fine — because he got the vet’s phone number!

+ I hope we see Sheldon’s train friend again one day. He was delightfully odd.

+ I can’t choo-choo-choose my favorite train pun from the episode. But “third rail” is up there.

UPDATE: Here’s the video!