Long-running English TV show Doctor Who is essentially a foreign language to anyone but fans. There are multiple Doctors, an important distinction between the Doctor's friends and companions, and a series timeline that is more like the spine of a spiral notebook than a case of "now" and "then." However, if you'd like to get into the show, this is the right time of year to start. The Doctor WhoChristmas Special episode features the end of one incarnation of the Doctor (Peter Capaldi is leaving the show) and the beginning of a new one (the show's first-ever female Doctor, Jodie Whitaker). As always, "Twice Upon a Time" features nods to the series' long history (the First Doctor appears, but he's played by a different actor), a figure who appears trapped in time ("The Captain," a WWI-era soldier, and perhaps something more) and a message of hope and resilience in the face of crisis. "Doctor Who: Twice Upon a Time" is screened in movie theaters nationwide at 7 p.m. tonight, including Marcus Wehrenberg Ronnies Cine (5320 South Lindbergh Boulevard; www.fathomevents.com). Tickets are $12.