What is 301 spoiler?

As an AI language model, I do not have access to specific plot details or spoilers. However, in general, a 301 spoiler could refer to a plot twist or a significant event that occurs in episode 301 of a television series. Spoilers are often avoided by those who haven't yet watched the relevant episode, to allow them to experience the story as the creators intended. It is important to refrain from sharing spoilers publicly and to give others a chance to watch the content without having key plot points spoiled.