Requirements: Must have Welch in your party. I also have three emblems, and Cyuss in my party, which is important for a choice you make partway through. In a FAQ I read, it says that Ronyx and Ilia come in, not Cyuss, so he's not a required element; on another playthrough, I'll get Welch and not Cyuss, and record the difference in dialogue for you all. Takes place in Tropp.
Format notes: For the emotes, I'm going to put them in (parentheses), and actions/exposition will be in italics. My own notes will be bolded. Also, since there's a crowd, assume (correctly) that there are multiple "Youth"s and "Young Lady"s.
Tropp. Roddick heads up into the main plaza to find a crowd of people gathered around Welch by the fountain.
Welch: Step right up, folks, step right up and marvel at my fabulous wares!
Welch: Here is my latest product for everyone! It's Welch Brand's very own love potion! Guaranteed to snare that special someone!
Youth: (!) Ooooohh!
Young Lady: (big sweatdrop) This looks really suspicious.
Youth: (musical note) No it doesn't! It's... it's the dream of every young man in the nation!
Young Lady: Oh really? Every young man in the nation must be pretty desperate, then.
Welch: (musical note) For one day only, I'm bringing you this love potion at a price that can't be beat!
Youth: How much is it, lady?
The screen begins shaking, and big exclamation points appear above everyone's heads.
Welch: I hope you're ready for this... all of this for only one Fol!
Young Lady: (big sweatdrop) Come on. This is getting seriously suspicious now.
Youth: Yeah... I'm not so sure about that price either.
Young Lady: (''') Why don't you drink it? Show us how it works!
Welch: (sweatdrop) Ooh... uh, I don't...
Youth: Yeah, drink it!
Welch: (scribbles) Mmm, what to do...
A choice comes up: "I got a bad feeling about this..." and "I should watch a little longer..."
>Choose "I got a bad feeling about this..."
Roddick: (big sweatdrop) ... I better get out of here. She's gonna make me drink that if she sees me.
Roddick leaves, and Cyuss enters. Welch spots him.
Welch: (''') Ooh, Cyuss! What perfect timing!
Cyuss: (''') Mm? What? ... Oh, you givin' that to me? Nice! I was just gettin' thirsty, actually.
Cyuss walks over, and we fade out. Fade in to Roddick, walking down the stairs to the entrance of the town.
If you walk back up, Cyuss is on his knees in front of the fountain.
Cyuss: I don't remember a thing about what happened...
Roddick: (big sweatdrop)
That's how it could've happened. But how about this? Choose "I should watch a little longer..."
Roddick walks up. Welch spots him.
Welch: (''') Ooh, Roddick! What perfect timing!
Welch walks over.
Welch: Whadaya mean, "ulp"!? C'mon, you aren't doing anything right now! Drink this love potion for me!
Roddick: Why do I have to drink that crazy stuff!? No, N-O, no way!
Welch: (angry dust-cloud) What's the matter, boy? My potion not good enough for you!?
Roddick: (sweatdrops) Well, who the heck would buy a one-Fol love potion!? Nobody, that's who!
Welch: I priced it for the sake of all the forlorn lovers in the world! Man, you really don't trust me, do you?
Roddick: It's not that. I'm just saying that I don't want to drink it.
Welch: You hate me, don't you, Roddick!? You're always so cold to me!
Roddick: (scribbles) Oh, all right, all right! Just stop crying! I'll drink it if it'll make you feel better!
Welch: (musical note) There you go! This would've been much easier if you had just said yes from the get-go.
Roddick: (big sweatdrop)
Roddick follows Welch over, back into the center of the crowd.
Welch: Gather 'round, everybody! This young guy is a total bust with the girls... but just one swig of this potion, and he'll be a changed man!
Young Lady: (''') Oooh!
Roddick: (big sweatdrop) *Sigh* Well, I guess it won't kill me. Here goes nothing!
Roddick drinks the potion. It... does not go down well.
Roddick: *Gulp gulp gulp* Gahhh! This tastes horrible!
Roddick: (sweatdrops) Urrrp... What's this stuff made of...?
Welch: (...) ...
Roddick: (angry dust-cloud) Ugh! I've just about had it with this... Welch.
His tone completely changes when he says her name, and his sprite turns pink as he walks closer to Welch, who sweatdrops.
Roddick: ... Why have I never noticed this before?
Roddick: Welch... My heart is full of untamed love for your soul.
Youth: (!) Oh ho ho!
Youth: (musical note) Whoa!
Young Lady: (sweatdrops) It really works!
Welch: Heh... uh... You see that, everybody? My love potion works instantly! It's absolutely the real deal!
Roddick moves closer to Welch, whose face turns red.
Roddick: Ahh... such a charming girl you are!
Welch: (heart) Oooh! You do go on, don't you? Please, not while everyone's watching!
Roddick's sprite begins to turn blue during the next line.
Roddick: I... I want to... I... I... I, iiiiiiiiiiiiii... Brrrrrrecccchhhh.
Welch: (!) Aaaaaagggghh!
Youth: Wow... That stuff must taste horrible.
Youth: Ugh... The girls would hate me even more if I drank that.
Youth: Yeah, you're right.
Everyone walks away, and Roddick - still blue - collapses.
Welch: (big sweatdrop) Hmm... Guess taste is more important than I thought. I think I'll make a strawberry flavor next time.
Welch gathers up her bottles and leaves. Fade out...
"An hour later..."
Roddick gets up and looks around.
Roddick: (sweatdrops) (scribbles) Ugh... where... where am I? Welch had me do something, and... I don't remember anything afterwards...