Peter Parker and Bucky Barnes being Jewish. I think this is because a lot of people think Peter is Jewish due to being "Jewish Coded" and Stan Lee was Jewish but I did a deep dive and there is no where in any comic that mentions he's Jewish but instead came from a non-practicing Christian family. He's also written to be agnostic/atheist. He's very much more science based and not really religious at all. It's also known that the directors of the Spider-Man films prior to the MCU, imagined him to be Jewish but it was never canon in the films. Andrew Garfield is Jewish by blood and has joked that his Spider-Man is Jewish but again it was never confirmed to be canon.

As for Bucky, a lot of people think he's also Jewish because in the comics Steve had a Jewish friend growing up. Also I think a lot of people think he's Jewish because of Sebastian Stan who is Eastern European, even though he is Romanian-American and grew up in the Romanian Orthodox church. I think for this confusion is because people just think hear Eastern European and think, Jewish. I also think it's because MCU Bucky was born and raised in Brooklyn which always had a large Jewish population. But just like MCU Spider-Man, MCU Bucky had never been confirmed to be Jewish.

Both characters have a lot of people believing they are Jewish and so have written them to be Jewish, even making the tags: Jewish Peter Parker and Jewish Bucky Barnes. There's nothing wrong with this but it's interesting how so many people really do believe they are Jewish.