Why ChatGPT suddenly couldn't stop talking about goblins?

OpenAI said ChatGPT repeatedly started referencing "goblins" in responses due to a bug. While training its latest AI models for "Nerdy" personality, OpenAI said it "unknowingly gave particularly high rewards for metaphors with creatures". "We retired the...personality in March after launching GPT-5.4. In training, we removed the goblin-affine reward signal," said OpenAI.