A while back, someone made a fanfic called Butterfly Kisses where Star grows large butterfly wings on her 16th birthday. In "Mewberty", after Star goes through her insect-phase and is back to normal, she ends up having wings. However, unlike Butterfly Kisses, Star's wings are much smaller and she can't really fly with them. Yet.
After "Blood Moon Ball", the lunar eclipse on September 27, 2015 that led to a real red moon practically became a meme for fans of the series.
Among Star and Marco's voice actors, Eden Sher and Adam McArthur, respectively, Sher doesn't ship their characters and considers Star and Marco to be Better as Friends, while McArthur is a massive Starco shipper. Come Season 2, Star is the one with a crush on Marco, while Marco only sees him and Star as Just Friends. It's basically the reverse of what their voice actors think about Starco.
"Running with Scissors" has Marco stranded in another world on an elusive quest, and becomes a Future Badass warrior on a motorcycle after many years of not having reached his goal. This gets rather hilarious when just one month later, the new season of Samurai Jack has its titular hero having done the same thing.
A fan created a Starco fanchild and gave her the middle name "Estrella" and a wand shaped like a pen. Many months later, more past queens of Mewni were revealed through a set of collectible cards. One of them had the name Estrella, and her wand appeared to be shaped like a pen. The fan took notice.
Someone made a fancomic about Star accidentally transforming Eclipsa into a baby. Then in the Season 3 finale Eclipsa turns her daughter Meteora into a baby, also by accident. This person was this close on predicting the outcome of the Eclipsa story arc.
The fact that Tom's dad is a mewman named "Dave" becomes hilarious after Satina became popular, whose father is a human named "David".
There is a Dimension Of Cats With Human Faces. Many are quick to compare it to the 2019 Cats Film, upon remembering said Dimension.
In the episode “Running With Scissors, while Marco is traveling through Heckapoo’s dimension, he adopts a “Dragoncycle” that he names “Nachos.” As the name implies, they’re dragons that have a body type (including wheels) that makes them be able to be ridden like a motorcycle. In Pokémon Scarlet and Violet: The player rides on a dragon (Koraidon or Miraidon depending on the version) that used similarly to a motorcycle.
where Star grows large butterfly wings on her 16th birthday. In "Mewberty", after Star goes through her insect-phase and is back to normal, she ends up having wings. However, unlike Butterfly Kisses, Star's wings are much smaller and she can't really fly with them. Yet.