The phrase "it might seem crazy what I'm about to say" is a notable quote from Pharrell Williams' 2013 song "Happy." It is used to introduce something that might sound surprising or unusual to the listener. The phrase sets a playful and positive tone, indicating that what follows may be unexpected but joyous or uplifting. The expression "might seem crazy" means "maybe it is crazy," suggesting a hint of doubt or surprise about the statement to come. This line has become popular and even viral, used to express absurd or notable statements, especially on social media platforms like TikTok.

In summary, the phrase is a catchy way to introduce a statement that may sound unusual or surprising, primarily known from the context of the song "Happy" by Pharrell Williams.