From I Love Lucy to Lost and everything in between, we're counting down TV's finest. Check out today's showcase of #20-11. Where does your favorite rank?

20. M*A*S*H
"Abyssinia, Henry" 3/18/1975
The much-watched finale eight years later made ratings history, but this was the episode that made M*A*S*H great. Before Internet spoilers doomed the element of surprise, millions of fans were stunned by the death of beloved Lt. Col. Henry Blake (McLean Stevenson). Slapstick scenes celebrating his Army discharge were capped by a coda that has yet to be topped by any sitcom: the news that Henry’s plane was shot down—no survivors—delivered by his bereft aide Radar (Gary Burghoff was handed the script pages only moments before filming). “It was one of those rare times on TV when somebody dies without any preparation,” recalls Alan Alda, who played Hawkeye Pierce. “All of a sudden, somebody you have an emotional attachment to is gone. [Producers] Larry Gelbart and Gene Reynolds wanted to give the audience the feeling of the suddenness of death in war. That was the thing: The show didn’t ignore the reality of war.”

19. THE OFFICE
“Diversity Day” 3/29/05
By its second episode, NBC’s remake fulfilled the order of Americanizing the classic Britcom The Office. Dunder-head Michael Scott (Steve Carell) puts his underlings through a sensitivity-training session. “It’s the strongest example of the kind of trouble Michael would get into,” exec producer Greg Daniels says. And a job well done.

18. THE ANDY GRIFFITH SHOW
“Opie the Birdman” 9/30/1963
After offing a mama bird with his slingshot, Opie takes her three orphaned nestlings under his wing. Should have known that kid would grow up fine.

17. SOUTH PARK
“Trapped in the Closet” 11/16/2005
Tom Cruise was the target, but Isaac Hayes is the one who felt stung: The former soul singer quit voicing Chef because of this ep’s Scientology jokes.

16. THE FUGITIVE
“The Judgment” 8/22/1967 & 8/29/1967
After four seasons and a final face-off with the one-armed man, the fate of Dr. Richard Kimble was watched by 72 percent of American households with TVs. Eat your heart out, Idol!

15. THE COSBY SHOW
“Goodbye Mr. Fish” 9/27/1984
Dearly beloved, we are gathered here today for the toilet internment of Rudy’s goldfish, Lamont. Death may not be proud, but it was hilariously handled here.

14. BUFFY THE VAMPIRE SLAYER
"Once More, With Feeling" 11/6/2001
The fantabulous but woefully Emmy-ignored musical episode still has people singing Buffy’s praises.

13. THE DICK VAN DYKE SHOW
"It May Look Like A Walnut" 2/6/1963
A sci-fi flick messes with Rob’s head and suddenly, we’re in a trippy adventure filled with a four-eyed Danny Thomas, walnut-eating aliens and an out-of-this-world closetful of laughs. The Sixties had begun.

12. SATURDAY NIGHT LIVE
4/22/1976
Writer Tom Davis remembers: “In my tenure as writer—1975 to 1980 and 1986 to 1994—I can’t remember another episode in which every sketch worked. All the other shows had one or two clinkers or muffed performances. In my book, Thirty-Nine Years of Short-Term Memory Loss, I call it the Best SNL Episode Ever. The whole week was free of disaster. Nobody was sick or depressed. Nobody was flying in on Friday from a movie set. Nobody was late for rehearsal. Nobody was dead yet. It opened with Paul Shaffer doing rock promoter Don Kirshner introducing a new act, the Blues Brothers. Steve Martin came out for the monologue doing a magic act, which required a volunteer from the audience—Bill Murray. We had a sketch with the Festrunk Brothers, two wild and crazy guys, and the poignantly hilarious ‘Dancing in the Dark’ sketch with Steve and Gilda Radner. And there was ‘Theodoric of York, Medieval Barber,’ conceived after I saw writer Don Novello in the hospital, his broken leg suspended by a rope and pulley, and I thought, ‘Let’s do a sketch about medieval medicine.’ But it was an idea Steve brought that set the standard. Lorne Michaels loved it and produced it to the hilt. The dancers, musicians—everything worked perfectly as Steve, in Pharaoh costume, stood and delivered the immortal words: ‘Born in Arizona. Moved to Babylonia. King Tut.’”

11. THE TWILIGHT ZONE
"Time Enough at Last" 11/20/1959
What’s worse than a nuclear blast? Broken glasses. There’s no other excuse for missing this classic.

Be sure to check out the rest of our list here:
#100-81
#80-61
#60-41
#40-21

The Paley Center for Media in Los Angeles is hosting screenings of select episodes of TV Guide Magazine's Top 100 Episodes! For more information, go to paleycenter.org/visit-daily-schedule/