So I got this little headcanon after reading the-potter-kids little story about how Jack and Eugene interact.
Disclaimer: I honestly don't own any of this.
"See you around Muddie" Jack flinched. The Slytherin took off in the opposite direction cackling.
"Aww" Rapunzel cooed "You have a nick name."
"Look again Punzie" Merida snickered "He has an embarrassing nickname. See his face is red!"
Hiccup and Rapunzel looked to confirm what Merida had said. "Seriously? They've been calling you Muddie since first year and you still blush every time " Hiccup said.
"I'm not blushing" Jack snapped.
Merida stepped in Jack's way and poked him in the face. "Then what do you call that?"
I, it's, see it's not" Jack floundered. He then turned to Rapunzel and grabbed her arm to drag her off "Come on Rapunzel, let's go to the library I need help with my transfiguration essay." Then they turned the corner, leaving Hiccup and Merida alone in the hall.
Merida ginned wolfishly and placed her arm on Hiccups shoulder to casually leaned on him. "Sooo" She said in as casual a tone as she could manage, "Do you know where he got the nickname?"
"Nope" Hiccup said as he stepped out from under Merida's arm. Merida lost her balance as Hiccup smiled.
"Want to help me find out?"
"I don't think I have a choice?"
Rapunzel and Merida were standing in the doorway to the great hall blocking traffic.
"Try flirting with Flynn" Merida urged.
"Flynn?" Rapunzel asked.
"Eugene, he prefers to be called Flynn and you're going to flirting with him so call him Flynn. Now I think I remember him calling Jack Muddie so I bet he knows where the nickname came from."
"I don't know Merida."
"You can flirt, can't you?" Merida challenged.
"Of course I can" Rapunzel huffed.
"That's what this is about?" an older Gryffindor shrieked. "Who is the guy? I'll help then you two need to get out of the doorway."
"Flynn" Merida answered.
"Eugene Flynn or another Flynn?" Asked the Gryffindor.
The Gryffindor turned to Rapunzel. "Take your wand our of your hair." The Gryffindor did that for her. "Pinch your cheeks to get some color in them." The pushy Gryffindor did that too. "Now when you go to talk to him sit really close. If you can sit in his lap. Other then that my only advice is try not to talk like you're a Ravenclaw."
"See you'll do fine" Merida encouraged. And because Rapunzel still looked reluctant she turned her around and gave her a shove in the right direction. Rapunzel turned to shake her fist at the Gryffindors, they only smirked and made little shewing motions before she very pointedly put her wand back behind her ear. But despite her reluctance Rapunzel turned on her heels, flipped her hair out of her face, and sauntered over to the Slytherin table. She would show both of them. She could flirt.
Back at the doorway the older Gryffindor coughed and held out her hand. Merida deposited a few knuts in the outstretched hand.
Jack saw her approaching and quirked and eyebrow when she didn't immediately head towards him. His mouth even hung open a little when she stood behind Eugene and placed her hand on his shoulder. "Hey Flynn" Rapunzel purred. "Hmm" Rapunzel leaned over Flynn's shoulder to look at his homework. "I was going to talk to you but looks like you have some work to do and unless I'm mistaken it's due after lunch."
Eugene's eyes were riveted to Rapunzel. "Nope" He said quickly as he slammed the book shut. "This isn't due for a while, just thought I would get it out of the way."
"Ah hah, I see" Rapunzel looked skeptical and her voice was still syrupy. Jack had stopped eating to watch the exchange. He knew Eugene liked Punzie, but Punzie liked Eugene back? That didn't seem like her at all. "Lets compromise." She grabbed the book and sat down backwards on the bench. "I'll help you work and we can talk."
After that Jack lost interest until, "So now I have a question, why do you call Jack Frost Muddie?" The Eugene's friends burst into peals of laughter. From the other end of the table Jack's head shot up and he glared.
"Well you see Blondie" Eugene reluctantly started to answer "It's an old inside joke. I don't really do in anymore. But the thing is you wouldn't get it."
"Oh" Rapunzel pouted. She glanced toward Jack. Jack had angrily stood up and was leaving the great hall. He passed Merida an the way out. She smiled and twiddled her fingers.
"See you around Muddie" She called after him. Jack didn't look back.
"But aren't you his best friend? Shouldn't you know everything about him? Why haven't you ever asked?" Merida had pounced on Hiccup after one of their shared classes.
"No I don't know everything about Jack. I didn't know him all that well when a few Slytherins gave him the nickname and by the time I was really good friends with him I had forgotten" Hiccup replied.
"Well you can ask him now?"
"So could you" Hiccup pointed out.
Merida groaned. "I can't. He knows I really want to know. So could you ask? For me. Please!"
Hiccup sighed. "Give Jack some credit, he'll know I'm asking for you."
"Could you try anyway?"
"What did he say?" Merida pleaded.
"Nothing. Told you it wouldn't work."
Even after a few weeks Merida still hadn't given up. Her plans and schemes had gone hill though. Most memorable was when she jumped on Jack's back. She though she would just ride around on Jack's back until he gave up. Instead Jack hadn't been ready to support her weight. The two of them took an unplanned tumble. Merida hit her head. Jack took her to see Madam Maudie. He didn't stop laughing the whole way. From that point on kept her attempts to verbal pestering.
"Won't you just tell me? Please Muddie?" Merida complained loudly as the four studied in the library.
"No" Jack refused.
"I'll stop asking" Merida whined.
"Of course you'll stop asking, you'll know."
"And I won't make fun of you."
Jack laughed cynically. "Like I'd believe that."
"But she will be quiet" Rapunzel spat angrily.
Hiccup groaned dramatically. "I'm not even sure I know what quiet is anymore."
"We wouldn't be having this problem if Muddie would just give in already." Rapunzel had started calling him Muddie also, but only when Jack and Merida's feud interfered with studying. "Are you afraid it will hurt your manly pride? It was funny for the first few days but now it's infuriating!"
Jack huffed and crossed his arms across his chest. "Talk to her then."
Hiccup made a keening sound and dropped his forehead into the table. "Just tell her already Muddie." It was the first time Hiccup had called Jack Muddie. The reaction was instantaneous, and violent. Jack stood up so fast his chair toppled over backwards. Jack grabbed Hiccup by the front of his robes and tossed him out of his own chair. The librarian heard the commotion and came running.
"Goodness gracious what is going on?"
"I tripped" Hiccup lied. "I tripped over the chairs and startled everybody."
"Oh alright then dear, If you're ok" She said.
"I'm fine." The librarian left and the other three converged on an unrepentant looking Jack.
"What was that?" Hiccup hissed. He tried to keep his voice low so they didn't attract anymore attention.
"You- you called my Muddie." Jack was so mad.
"Yeah, so" Hiccup growled "The girls have been doing it for weeks."
"Exactly" Jack explained "It's the girls."
"Hey" Merida cried "Are you saying you won't hit us because we're girls? But you'll throw Hiccup around any old day because-"
"It means mudblood" Jack interupted.
"What?" Merida chocked.
"Muddie means- When they call me Muddie they'recalling me a mudblood." Rapunzel gasped and covered her mouth. Merida's face burned in shame. Hiccup tried to put his hand on Jack's shoulder but Jack shrugged him off and gather up his books. "I think I'll head back to my common room." Jack left.
"Hey Muddie" Eugene called "Your friends are waiting outside for you."
"Well they can wait all night for all care, so thanks but no thanks Eugene."
"Well I would rather I never had to hear your voice again. We can't all get what we want."
Eugene backed off for a second. "Wow, who put bees in your bonnet?"
"What did you just say-" Jack hissed.
"Come on grumpy gills. If I get you outside Blondie promised me a kiss." Eugene grabbed Jack and hauled him out of his chose armchair in the common room
"Hey" Jack yelled "Let go. I don't want to talk to anyone."
"Tough." Eugene tossed Jack out of the common room. "Do I get my kiss now Blondie."
"Fine Eugene, come here." She gave him a little peck on the cheek. Eugene didn't even look disappointed. As soon as he was gone Hiccup, Rapunzel, and Merida pounced on Jack.
"That's just awful" Rapunzel said "Why haven't the professors done anything?"
"They're Slytherins, they're not dumb enough to call me -that- when a teacher is around."
"Then complain" Merida implored "Don't just sit there and take it, tell someone!"
"I did!" Jack cried "but again they're Slytherins. They hide their insults under cute nicknames. The professors aren't going to notice not if my best friends can't"
Silence fell. "Jack" Hiccup hesitated "We are really sorry."
"No I'm sorry" Jack said. "I shouldn't have said that. It wasn't fair to you guys."
"But we should have noticed" Merida said "And we didn't. So let us try and help you. I don't care how many detentions I get I'll hex anyone that even thinks about calling you -that-"
"I'll help" Hiccup offered.
"Here here" Rapunzel called out before initiating a group hug with Jack in the middle."