Justice League x RWBY: Super Heroes and Huntsmen Part One

Justice League × RWBY: Super Heroes & Huntsmen is a 2023 two-part American direct-to-video animated superhero crossover fantasy film loosely based on the limited crossover comic book series RWBY × Justice League and DC/RWBY written by Marguerite Bennett. The films are a co-production of Rooster Teeth Productions, DC Entertainment, and Warner Bros. Animation, the film centers on several members of the Justice League mysteriously turned into teenagers and teleported to Remnant while teaming up with Team RWBY to defeat a superpowered Grimm and a group of supervillains, including an old enemy of RWBY.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.