The Twilight Zone has not been, in any of its incarnations, about making people laugh, but the 80's revival managed one Funny Moment with its short "I of Newton", in which Sherman Hemsley finds himself confronted with Ron Glass's devil..
The devil's ever-changing message T-shirt: "Hell is a Summer Festival," "Hell is a City Much Like Newark," "Over 100,000,000,000 Served," "Gehenna: More Than a Place, a Way of Life," and "Let's Do Damnation."
And exchanges like this:
Sam: Yeah, well you can just go back to whatever Stygian depths you came from, fella. Because I have no intention, thank you, of selling my soul for the solution of any equation!
The Devil: "Stygian depths." I like that. You mention Dante to most people these days, and they ask you how you liked Gremlins.
In "A Penny for Your Thoughts", the hero is testing out his newfound mindreading powers on the people he sees. He briefly pauses on a grinning pretty lady who is fondling a pile of money and giving off absolute silence.
Need we mention that the pretty lady happens to be blonde?!
The hero overhears a Jerkass co-worker thinking unsavory things about a secretary, who our guy happens to like. The hero responds to this by pouring some water on him.
Jack Elam's character in "Will The Real Martian Please Stand Up?" steals the spotlight.
The parrot in "Four O' Clock", who calls his owner, a Troll who harasses people he deems "evil", a nut.
The last scene of "A World of His Own". Rod Serling, usually an invisible narrator, is monologuing the outro, describing the story as "ridiculous nonsense" that could never really happen, when the main character (who is able to create fictional characters by describing them into a tape recorder and destroy them by burning the tape) gets upset at Rod, and puts a tape labelled "Rod Serling" onto the fire. Serling says "Well, that's the way it goes," and fades away.
What makes this really funny is that this was the first time on the series that Serling ever appeared on-screen in the show.
At the end of "A Most Unusual Camera", the way the French bellhop screams as he falls out the window gets me every time. It really sounds like it belongs more to someone being shot out of a catapult in Holy Grail.
"One For The Angels", where The Grim Reaper goes nuts buying ties and string from a pitch man.
In the 80s revival episode "Dealer's Choice", a group of friends playing cards believe that the stranger in their group is The Devil (note that they live in Newark):
"What's he doing here?"
"What do you mean? I think he lives here!"
I find the Mood Whiplash in "The After Hours" hilarious. Within the course of five minutes at most, the mannequins go from scaring the crap out of Anne Francis, to making her realize that everything she thought about herself was a lie, to bidding fond and cheery farewells to the saleswoman mannequin as she goes to live among the humans for one month.
Many, many examples of the closing narration. Take "What's in the Box"
The next time your TV set is on the blink, when you're in the need of a first-rate repairman, may we suggest our own specialist? Factory-trained, prompt, honest, twenty-four-hour service. You won't find him in the phone book, but his office is conveniently located—in the Twilight Zone.
"The Whole Truth". A stock dishonest car salesman is sold a car that makes him physically incapable of lying. Hilarity ensues, as does the end of the Cold War when he manages, by way of selective omission, sell the Model A to Nikita Krushchev.
"Once Upon a Time" is set in 1890 and 1962. And the 1890 segments are done as silent films.