If you are asking about how to format a for this specific movie, it was not released with an official subtitle (like "There's Something About Mary: [Sub-title]"). However, it is often discussed in the context of the "Gross-out Comedy" genre. If you'd like, let me know:
Are you trying to find a (e.g., "Love is in the hair")? subtitle There's Something About Mary
Do you need help that includes this title? If you are asking about how to format
In standard title capitalization (Title Case), "There's" is capitalized as the first word, and "Mary" is capitalized as a proper noun. The word "Something" is also capitalized as a principal word, while "About" is typically capitalized in titles as well. subtitle There's Something About Mary