The phrase "crazy stuff" is an idiomatic expression that refers to unusual, unexpected or unbelievable events, actions or situations. It can be used in a positive or negative context depending on the speaker's tone and intended meaning. For example, someone might say "I can't believe he did such crazy stuff!" to express disbelief or disapproval of something that happened. On the other hand, someone else might use it in a more lighthearted way by saying "That was some crazy stuff we pulled last night" to describe an exciting and memorable experience.