Odd world generation

Very unique world errors. I had a 2x2 chunk space, then it got corrupted, he chunks were present but they were flashing though, showing caves, different biomes, and strange entities that were very large. I have no present mods.
When my little bro connected through LAN, His player model was an arm.
Help? I only have this screenshot, the rest of the weird flashing chunks are recordings. Too heavy to post