Creators of Super Smash Flash Making an Official Indie Crossover

Fraymakers looks to be the most ambitious indie crossover fighting game yet, with a successful Kickstarter campaign that is still ongoing.
Successfully funded on Kickstarter!

Indie Tournament! (An Indie Smash Bros Game) Fan Casting for Make your Own Crossover

JOLLY J✨ on X: @MTLSaiyan How about a 2D Style / Smash Bros Styled Crossover Fighting game FOR INDIE CHARACTERS! I'm talking Cuphead, Shantae, Meat Boy, Steve, Sans, Celeste ETC going head

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Fraymakers Preview – A Fun Indie Smash Bros Might Finally Arrive, Just Not Now

Fighting for Recognition: The History of Fighting Game Crossovers

Why Smash Fans Should Be Excited for Fraymakers

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Super Smash Bros. has become 'Video Games: The Video Game' – Destructoid

Fraymakers (Steam) Early Access Impressions — Forever Classic Games

crossover with indie characters (what do you think?) : r/ShovelKnight