Katy Perry & Allison Williams
Unlike most of the celebs on this list, Perry and Williams met through mutual friends rather than working on a project together. Everyone knows Katy Perry as the pop sensation who brought us hits like “I Kissed A Girl” and “Dark Horse,” and everyone knows Williams from her role in Girls, but not everyone would immediately pair these two as besties. The reason for this is the pair’s desire and appreciation for privacy. They rarely post about each other on social media, but they can frequently be seen going out and having a great time together. Maybe that privacy is the key to a long-lasting friendship!