On this day in 1988, TV viewers saw one of the most famous — and perhaps the most debated — series finales in TV history. The episode marked the end of St. Elsewhere, an NBC drama about St. Eligius, a run-down Boston hospital headed by chief of staff Dr. Donald Westphall (Ed Flanders). His staff included Dr. Daniel Auschlander (Norman Lloyd), Dr. Mark Craig (William Daniels) and various young interns and residents.  

During the show's six seasons, the show divided it focus between weekly medical cases and its employees' personal dramas. Its ensemble cast included Ed Begley, Jr., David Morse, Howie Mandel, Terence Knox, Denzel Washington, Mark Harmon, Christina Pickles, Stephen Furst, Alfre Woodard and Bruce Greenwood.

At the tail end of the final episode, viewers see an exterior shot of the hospital, with snow falling all around.  The next scene shows Donald Westphall's autistic son, Tommy (Chad Allen) playing with a snow globe. Westphall enters, and the scene makes it clear that he's not employed as a doctor. A conversation reveals that Auschlander, who's also present, is Westphall's father.  The two discuss Tommy, with Westphall lamenting that his son does nothing but sit and stare at the snow globe. Westphall then takes the globe from Tommy, and tells him to wash his hands for dinner. When he places it on top of the television, viewers see a tiny replica of St. Eligius hospital, surrounded by swirling snow - implying that the show's entire six seasons were merely the imaginative musings of an autistic child.

Following the finale, a "Tommy Westphall Universe" hypothesis was developed, inferring that numerous television shows were, in fact, dreamed up by Tommy and exist only in his mind.

Want to re-visit St. Eligius? Here's the complete pilot episode: