”It’s Always Sunny in Philadelphia” creator and star Rob McElhenney was back at his alma mater St. Joseph’s Prep yesterday touring the school’s new building. McElhenney, a 1995 Prep grad, is close friends with the Prep’s Dean of Students Dennis Hart. The actor gave an impromptu talk (in English) to a Spanish class, signed autographs and took pics with students. McElhenney, a South Philly native has been very generous with the Prep over the years, donating a walk-on role on “It’s Always Sunny…” to the school’s annual “Hawktion” fundraiser for the past few years.