excuse me, i had this question and wanted to ask (because the rules says nothing) its ok to make a game with a theme or characters from a lnown franchise, like a series, anime, or game? like a fan game, is there any problems with that? thanks in advance

Personally I'd avoid treading on existing IPs. I doubt the company who owns it will come after your jam game, but it's still better to use original work. You may even want to expand on it after the jam and sell it. You can't do that if you're using copyrighted assets in a universe that is not your own.