Pen, Paint, and Pretzels, the umbrella organization for student-run performing arts groups at Tufts University, presents the first of three performances of “Startling,” its fall semester Main Stage show. Written and directed by Max Bennett; stage managed by Alexa Hopwood. Open admission; no tickets required. The show will be repeated at 8 p.m. on Friday, December 2, and at 3 p.m. on Saturday, December 3.