So apparently it was a thing for the seniors to wear all kinds of crazy stuff for their senior pics. Some were wearing wigs and crazy clothes. Kristen opted for her favorite Grandma sweatshirt. Seriously, she wears it all of the time.
Anyway, she is now immortalized in it.
Apparently after the photographer finished taking pics of Kristen's group of students, they wouldn't let the seniors do any more crazy pics.