海绵宝宝是派大星的闺蜜派大星是海绵宝宝的闺蜜
[hăi mián băo băo shì pài dà xīng de guī mì pài dà xīng shì hăi mián băo băo de guī mì]
This comes from popular cartoon characters - SpongeBob SquarePants (海绵宝宝) and Patrick Star (派大星). Calling each other best friends expresses closeness. However, 'best friend' usually applies more between the same gender while here '闺密' implies female-only friendships which adds a layer of non-traditional humor