Joke Gone Awry

S. has staged an elaborate practical joke of some kind, the aim of which is to photograph me either holding a wooden stake or appearing to be staked (as if I were a vampire). In aid of this he and an accomplice lure me into some kind of academic office building, where everyone is in on the joke. They chase me around and try to capture the desired photo. When I finally realize the plot, I am indignant and hurt. Why would S. do this to me?