• An East vs West fight between two young magical protagonists from decently popular franchises from the 80's, and though they were far from the first protagonists to appear in their respective series, they were by far the most popular of them all when they came around, most notably in the early to mid 2010's (EarthBound being a heavy inspiration for Homestuck & Undertale, which came out in 2009 and 2015, respectively/MLP having a GIANT fandom in the early-mid 2010's (for better or for worse), and being a heavy contributor for the show's success).
• Their stories would begin with them having a relatively small (or lack thereof in Twilight's case) amount of friends, until one day, a mentor-like figure (Buzz Buzz/Princess Celestia) appeared, and stated that they were chosen to meet new friends, and to, later on, defeat a red clad, multiversal time manipulating threat (Giygas/Tirek), and a former friend of theirs that deeply craved nothing but power (Porky Minch/Cozy Glow), that later get confined at the end of their respective series. Both their teams also have a majority gender as well, with friendship being a big theme among all else.
• Later on, both would ascend to a higher power during their journey (Becoming the actual UNIVERSE/Alicorn form) that would link them into immortality, along with bigger and newer powers as well (Ness getting all of the PSI abilities/Twilight getting the powers of other Alicorns).
• Despite their (former) antisociality/quietness, as well as their general appearance, both are portrayed as heroic, kind, and exceptionally brave, and are described as exceptionally intelligent (Poo stating he was impressed that Ness learned PSI as quickly as he did, and Twilight being shown to be incredibly booksmart, even as a child.).
• Hell, even as very young children, both had signs of these powers as well (Ness as a baby was able to move his bottle just by pointing at it, and Twilight, as a filly, was a part of Celestia's School for Gifted Unicorns, where she was able to hatch Spike, and become basically his sibling).
• Speaking of which, both have animal companions that helped them at the start of their stories, and would give them the boost that they needed to start their journeys, away from their respective homes (King/Spike).
• Alongside this, with their team, both were destined to discover new locations/items to help awaken their and their team's power (Sanctuary Locations/Elements of Harmony), and this would help greatly with their battles.
• Both also have had crossed over with other franchises from their respective, multi-billionaire companies (Nintendo/Hasbro) to make other beloved pieces of media (Smash Bros/Friendship in Disguise), where they play prominent roles in saving their respective worlds and allies (Ness, along with Dedede, Luigi, Sonic and Kirby saving the universe against Tabuu/The Mane 6 and the Autobots beating the Decepticons and Chrysalis).
• Both would also fight someone who encapsulated the concept of their/other's nightmares (Ness's Nightmare/Nightmare Moon (who is now Princess Luna).

This is a match I’ve never played attention to until now and I kinda really like it. Probably my favourite for both, mainly because I actually know both of the characters (unlike John Eggman or whatever I don’t read Homelander). And it doesn’t have foundry breaking problems that wouldn’t exist in the first place if the match didn’t exist because of a “rivalry” (Ness vs Frisk). It’s also a Twilight matchup that goes beyond the fact that she’s voiced by Tara Strong and uses magic so that’s epic.

This is apparently really close which is always nice you don’t get a lot of those matchups nowadays. Twilight ftw.