When NBC’s hour-long hospital drama St. Elsewhere signed off after six seasons on May 25, 1988, more than a few viewers were saddened. Not necessarily because the series—which had earned 13 Emmy Awards during its run—was ending, but because producers opted for a highly unconventional finale. In the closing moments of the episode, a boy named Tommy Westphall (Chad Allen), the son of medical director Dr. Donald Westphall, was seen peering into a snow globe. Inside the globe was a tiny mock-up of St. Eligius, the medical center that was featured in the series. Behind him stood his father, who was sporting a construction worker’s wardrobe.

The implication was that Tommy—a character on the autism spectrum—had imagined the entire show, a fiction-within-the-fiction conceit that had angered viewers during the infamous “dream season” arc on Dallas five years earlier. (On that series, Bobby Ewing was brought back to life after his "death" turned out to be just a bad dream.)

“I expect a very mixed reaction,” Bruce Paltrow, one of the show's executive producers, told the Chicago Tribune in 1988. “I think some people will think it's extraordinary and existential and quintessential St. Elsewhere. I think other people will find it puzzling, odd, maybe unfulfilling in some way.”

More than puzzling, some people found it to be an actual puzzle. If the universe of St. Elsewhere was a figment of Tommy Westphall’s elaborate imagination, then wouldn’t other television characters who appeared in the show’s continuity exist only within Tommy's mind, as well? The doctors had visited the bar on Cheers in one St. Elsewhere episode; Cheers spawned Frasier, a character who appeared on Wings; John Munch, the detective from Homicide, had mingled with the St. Eligius crew, and he has appeared on shows ranging from The X-Files to The Wire, effectively making him the Patient Zero of what's become known as The Tommy Westphall Universe theory.

As of this writing, 441 shows can be tied to St. Elsewhere with varying degrees of separation, ranging from I Love Lucy to The Flash. If the theory holds, then a large chunk of television is the direct result of one child’s formidable imagination.

St Elsewhere Full Episodes, YouTube

Erasing the fiction of an entire medium is not what Tom Fontana had planned. One of the producers on St. Elsewhere, he was openly hostile toward any idea of a reunion special down the line and insisted that the series finale should be definitive.

Fontana’s favored conclusion was a literal apocalypse, where the staff of St. Eligius would be standing by in the year 2013 while a toxic gas cloud passed over, the result of a corporate war between foreign factions. When NBC refused to finance their ambitious plan, the idea for the snow globe was hatched. (Quizzed by IndieWire in 2012 as to who exactly came up with the idea, neither Fontana nor co-writers Channing Gibson or John Tinker could remember.)

Fontana did, however, recall that half of the viewer mail retrieved after the finale was positive, while the other half made loose reference to a desire to “burn [the studio lot] to the ground."

Fontana went on to create Homicide: Life on the Street and HBO’s groundbreaking prison drama Oz. Those two impressive achievements would have likely relegated the bizarre ending of St. Elsewhere to a trivial mention in Fontana’s biography, if not for the curiosity of a playwright named Keith Gow.

Gow, a resident of Melbourne, Australia, spent time in pubs and online wondering what Tommy’s scene meant for every show connected to St. Elsewhere's characters. "The discussion began on alt.tv.homicide, a newsgroup that discussed Homicide: Life on the Street," Gow tells Mental Floss. "[Fontana] was fond of putting in references to previous shows he worked on, including bringing characters from St. Elsewhere into Homicide."

Along with U.S.-based fan Ash Crowe, Gow began to develop a chart linking the series to other shows on television. Over time, it began to look something like the Six Degrees of Kevin Bacon game.

Here’s how St. Elsewhere links to Doctor Who [PDF], hypothetically rendering the TARDIS a figment of Tommy’s imagination:

Donald Westphall and two other doctors visited Sam Malone’s bar from Cheers; Cheers introduced Frasier Crane, of Frasier; John Hemingway of The John Larroquette Show once called into Frasier’s talk show; The John Larroquette Show once mentioned Yoyodyne, a manufacturing client of law firm Wolfram and Hart; Wolfram and Hart had another client, Weyland-Yutani, that made a weapons display screen for Firefly; A Weyland-Yutani ship is seen in the BBC series Red Dwarf, which also depicted The Doctor’s TARDIS.

A sampling of the Westphall grid. Courtesy of Keith Gow

These strings go on across multiple decades of television, with I Love Lucy being the earliest example. Often, characters crossing over on the same network can ignite a connection, with shared brands or locations providing the connective tissue for others. The fictional Morley cigarettes are particularly pervasive, as is Hudson University, an institution of higher learning mentioned on The Cosby Show, Law & Order, and Murder, She Wrote.

"I prefer character connections, myself," Gow says. "That really solidifies things. And most of the connections on the grid are characters, even though something like Morley cigarettes (a fictional brand) has a lot of individual connections, they just add to the connective tissue in certain ways. The fictional brand or company thing is also Fontana's fault. The corporation that bought St. Elsewhere in its final season owned the prison hospital in his series Oz."

Over time and with the help of reader contributions, The Tommy Westphall Universe grew to include shows as diverse as ALF, The Fresh Prince of Bel-Air, Knight Rider, Melrose Place, Seinfeld, and dozens of others, much of it helped along by the character of Munch appearing in more than 10 series, and those series making reference to other characters and brands.

As Gow and Crowe assembled their chart, comics writer Dwayne McDuffie (Static Shock) wrote a blog entry for Slush.com in 2002 that made a similar observation. "St. Elsewhere also shared characters with The White Shadow and It’s Garry Shandling’s Show,” McDuffie wrote. “Garry Shandling crossed over with The Andy Griffith Show (no, really!). So Gomer Pyle, U.S.M.C., Mayberry R.F.D., and Make Room for Daddy/The Danny Thomas Show are gone. Make Room For Daddy takes out I Love Lucy.”

All of it, McDuffie said, proved his own Grand Unification Theory that everyone and everything seen on TV—except for the few minutes viewers spent with Tommy Westphall in May 1988—is just a daydream.

St Elsewhere Full Episodes, YouTube

As one of the co-authors of the scene that ignited the entire premise, Fontana said he was “stunned” to discover the aftershocks and that the theory “basically means that Tommy Westphall is the mind of God.”

Fontana was being facetious (we think), but not everyone was as enthused with the premise. Observers of the theory take issue with the idea out of what they deem is a misunderstanding of an author’s intent. While the doctors of St. Elsewhere visited the Cheers bar, the creators of Cheers offered no consent to have their series thought of as imaginary. There’s also nothing standing in the way of the belief that perhaps the Tommy Westphall end sequence was itself a dream, negating the snow globe conceit. And what about the real people who have appeared on the included shows, like Alex Trebek on Cheers? If Cheers is not “real,” then is Trebek?

But the notion isn't necessarily dependent on Tommy imagining anything: The connections still exist, whether they're considered a dream within fiction or just an interconnected television universe. "The theory doesn't really depend on Tommy Westphall, but he's a good hook," Gow says.

Gow and Crowe, who still periodically update the grid, assert that episodes with real people playing themselves—like Trebek did on Cheers—are exempt, as are cartoons and feature films. That would surely lead to spreadsheets the size of walls: Weyland-Yutani is the company behind the machinations of the Alien franchise.