MultiVersus is already being modded, with one player managing to add in Rayman, Goku, and Minecraft's Steve.
Twitter user junior3DM shared a few videos and screenshots on their Twitter page that show that they've already begun modding MultiVersus. The first video shows . It fits surprisingly well, especially considering junior3DM actually animated some of Steve's movements themself, which they revealed in a later Tweet, "I just animated a bunch of stuff myself cause I mean its minecraft so its pretty easy also idk why the sword is doing that".
The next mod that junior3DM has created is one that . The Rayman model actually looks like the fake Smash leak that was going around back in the early days of Smash Ultimate. It's such a good conversion that the only way to tell which character Rayman replaced is through the idle animation, which makes it clear that it's Jake.
The final character mod that junior3DM showed off is actually pretty fitting - . Considering Shaggy is based off of the Ultra Instinct Shaggy meme, a move taken directly from Goku, it's the perfect character swap. Unfortunately, we've only got the one image for his one as the modder didn't post a video.
If you want a mod that's a little more official, junior3DM also revealed that as a skin for Finn from one of the earlier MultiVersus playtests. Similarly to how Jake has a skin that makes him look and sound like Cake, Finn has one that changes him into Fern, although it reportedly didn't change his voice in earlier versions of the game. It was removed from this version of the game, but has now been restored thanks to junior3DM.
It seems that it's not just one skilled modder making changes to MultiVersus either, . This is despite the fact that the game apparently has easy anti-cheat, which has led to some confusion about how mods are being allowed.