If you have to go to the prom, you may as well get a souvenir from that memorable evening. These cops took advantage of the amenities, including having their portrait made. No photographer is going to tell them they can't pose for a picture!
For readers outside the U.S. or without kids, police are often assigned to attend the prom in order to keep students from driving away drunk, although they sometimes have to break up fights or deal with more serious crimes. -via reddit