Stay with me now, this is complicated but kind of fun.
Characters from St. Elsewhere have appeared on Homicide, which means that show is part of the autistic child's daydream and likewise doesn't exist. It gets worse. The omnipresent Detective John Munch from Homicide has appeared on X-Files, Law & Order and Law & Order: SVU. Law & Order characters have appeared on Law & Order: Criminal Intent. X-Files characters have appeared on The Lone Gunmen and Millennium. Characters from Chicago Hope have appeared on Homicide. Characters from Picket Fences have appeared on Chicago Hope. All those shows are gone (if you count cartoons, which makes this game much too easy, the X-Files characters have appeared on the Simpsons. The Critic has also appeared on The Simpsons. Dead).
Characters from Picket Fences have appeared on Ally McBeal. Ally McBeal has appeared on The Practice. Characters from The Practice have appeared on Boston Public. Autistic daydreams, every one.
But that's not all. St Elsewhere characters have appeared on Cheers, so Fraiser doesn't exist. Neither do Wings, Caroline In The City or The Tortellis but who cares? Well, maybe you do, because Caroline In The City once crossed over with Friends, which crossed over with Mad About You, which crossed over with Seinfeld and The dikk Van Dyke show. None of them happened in our new, shared continuity.
St. Elsewhere also shared characters with The White Shadow and It's Gary Shandling's Show. Garry Shandling crossed over with The Andy Griffith show (no, really!). So Gomer Pyle, Mayberry RFD, and Make Room for Daddy/The Danny Thomas Show are gone. Make Room For Daddy takes out I love Lucy.
And there's more, St. Elsewhere also shares continuity with M*A*S*H, so Aftermash and Trapper John MD are out of there.
Now here's a good one, St. Elsewhere shared a patient with The Bob Newhart Show, so the Bob Newhart Show is part of the grand daydream. The Bob Newhart Show crossed over with Murphy Brown, which in turn links to, among many others, Julia, The Nanny, Everybody Loves Raymond and I Dream of Jeannie!. Meanwhile, the series Newhart was revealed to be a nightmare had by Bob Newhart's character on the Bob Newhart Show. Newhart crossed over with Coach, which connects it to Grace Under Fire, Ellen and Drew Carey. Drew Carey takes out Home Improvement and NYPD Blue.
All of these shows (and many more that I left out or missed) are daydreams of St. Elsewhere's autistic kid.
This is by no means an exhaustive list. Links to the Happy Days, All In The Family and Diagnosis Murder universes would take out another 20 or 30 shows. If we can get to The Mary Tyler Moore Show, who knows how many would fall? My favorite possibility? A link to Knight Rider, of all things, would remove every single Star Trek series. I wouldn't mind some research help from my vast and loony readership on these and any other shows you guys can think of, E-mail me. No cartoons though, that way lies madness. The Scooby Doo movies alone encompass a good chunk of the space/time continuum.