Okay, trying to get back in the fanfic-writing saddle. Here's the previously mentioned Star vs the Forces of Evil story, part 1 of until I get bored of it since it's meant to be a funny domestic thing that doesn't really have an ending.
1. Honeymoon's Over
It had been over a decade since Star Butterfly first came to Earth. As the years passed, and her fondness for Earth and especially the people on it continued to grow, Star constantly found excuses to convince her parents she should stay for just a little longer.
It couldn't last. By the time she had graduated college, Star knew her time on Earth was getting ever closer to its end. Marco realized this too, and while he had been planning it for months, it was the fear of Star leaving that gave him the final push to propose.
The news went over far better with King and Queen Butterfly than either Star or Marco had expected. Not to say there wasn't a great deal of resistance, the princess of Mewni marrying a commoner would have been scandal enough, let alone that he was from another dimension, but but the pair had expected far worse.
King River had a lot to do with that, he'd already considered Marco family for years, and by the time Star and Marco were in college, Queen Moon had resigned herself to the inevitable as well.
Between the joy over getting married and the struggles to legitimize it, Marco never fully realized one of the consequences of marrying Star until far too late...
A dimensional portal opened in the throne room, the King and Queen shifted all attention to it with baited breath. As a figure stepped through the portal their suspicions and hopes were confirmed, Star and Marco had returned from their cross-dimensional honeymoon.
Marco was carrying Star bridal style, while Star waved both of her hands. "Hi Dad! Hi Mom! I'm waving for both of us because Marco doesn't have any free hands!"
"Your majesties," Marco said, the beaming grin on his face saying the rest.
"Starling!" King River ran to his daughter, who leaped from Marco's arms for a hug. River did one better and caught up both Star and Marco in his crushing embrace. "Don't think I forgot you, Marco, or should I say, son?"
"Huuuuuuuuugs!" Star squeezed her arms tighter around her father and her husband. Something was missing though. "Mom? Come on, you're missing the hug party!" Moon reluctantly joined in on the group hug.
"So how was your honeymoon?" King River asked as the four separated.
"AMAZING!" Star bounced in place recalling the experience.
"Yeah, definitely," Macro agreed. "I still can't get over that there's an entire universe that's just a hotel. Or the beach where the sand was made out of cotton candy,"
"Yeah that was pretty great, especially the cotton candy sandcastle building competition," Star interjected. "Oh, and the penguin-sledding! And the ultimate battle-couple fighting championship, and the dinosaur zoo... But nothing beat the club that served those pan-galactic gargle blasters!"
"Ha, that entire day is just a blank space in my memory," Marco paused. "They were kidding about the side effects, right?"
"I dunno," Star shrugged.
"Anyway, thanks again for setting this all up," Marco smiled at the King and Queen.
"Well this was nice but we better get going," Star gestured to the portal. "We're going to visit Marco's parents, then Princess Pony Head invited us to a honeymoon after-party which I don't think is something that actually exists but it sounds awesome-"
"Actually you're not going anywhere." Queen Moon stepped in front of the portal.
Star's near perpetual smile dropped. "Whaaa?"
"Is something wrong, Queen Butterfly?" Moon's face remained blank, "Mom?" Marco offered instead but Moon's expression was unchanged. "Uh, I'm not really sure which you'd like for me to call you now? Queen Mom?"
"Marco Butterfly-Diaz, soon you are going to be the King of Mewni. There's much you have to learn and little time to teach you."
Before Marco could answer, Star got between him and her mother. "Aw come on Mom, you and Dad have at least five, maybe ten years of ruling left in you. We don't need to do this now."
Marco put his hand on Star's shoulder. "It's alright, Star. Queen slash Mom has a point. I could use a short introduction on how to rule."
"Nothing about this introduction is going to be short. Star has been groomed to be queen of Mewni for her entire life. We're going to have to condense a whole childhood's worth of instruction for you," River added.
"But we have jobs, I teach karate, Star's..." Marco paused, trying to explain the situation without bringing up anything Star wouldn't want her parents to know about.
"I'm... between jobs. The fabric store never forgave me for the little accident with the silk-snakes and wool tornado." Star leaned closer to her mother, "I think she was just looking for an excuse to fire me."
"We can't just drop everything and stay here yet; what about if I came to train on the weekends?" Marco suggested. "I'm a fast learner, after all I got straight-A's throughout high school and college."
"Do you know anything about royal etiquette?" River asked.
"How to issue a royal edict?"
"The cultural climate of Mewni?"
"Our laws and different functions of government?"
"What to do in a state of emergency or war?"
"The nations we maintain diplomatic relations with and how to handle those relationships?"
"What the different roles the king and queen perform in Mewnian society?"
"That's enough, dear," Moon said. "I think Marco understands now why this isn't something he can learn 'on the weekends'."
"Marco is going to be a great king," Star interrupted. "Besides, he's got me to show him the ropes."
"That's exactly what I'm afraid of."
Star wanted to argue the point further, but couldn't come up with anything else in her or Marco's favor.
"Can we at least visit my parents first?"
Moon nodded to Marco's request. Star cut a new portal with her dimensional scissors, this time to the Diaz residence, and the newlyweds disappeared into it.
"What are the odds they make a run for it and don't come back?" Moon asked rhetorically.
"Wouldn't surprise me, we tried the same after all," River chuckled. "I have a feeling Marco will talk her out of it, though."
"That's why I let Star marry him," Moon smiled.