"Three Little Piglets" is simply the funniest episode of the series, or any Winnie-the-Pooh series, for that matter. Pooh tries to read the story of the Three Little Pigs, but he and Tigger goof around with it in every way imaginable: Pooh continually attempts to insert honey into the story, the wolf becomes an annoyed Rabbit wearing a Big Bad Wolf costume, he mistakenly mixes in elements from other fairy tales ("the Big Bad Bunny was going to see his grandmother..."), the house of sticks becomes a house of cards, Tigger tries to save the pigs as the Masked Offender, and finally, Rabbit ends up getting drenched by a honey eruption.
Tigger's failed attempt to protect Rabbit from broken-mirror caused seven years of bad luck in "Luck Amuck" results in Rabbit getting buried under a mountain of watermelons (long story) - leaving Tigger to dig him out. Pooh comes across this crazy scene with his usual oblivious friendliness - which makes the following sequence ludicrously funny due to how totally unfazed and immediately accepting he is of the absurdity even while Rabbit is freaking out in front of him.
Pooh: "Tigger what are you doing?"
Tigger: "I'm digging for rabbit, Pooh-boy." <Tigger unearths Rabbit's head>
Pooh: "Well, you're in luck!" (cheerful chuckle) "There's one now!"
Rabbit (in the middle of an epic Freak Out): <insane sobbing/laughter> S-seven more years! <insane sobbing/laughter>
In scene where Tigger decides to run away so he wouldn't harm anyone with his bad luck, he puts ludicrous items in a trunk to move away with, including a sewing machine, Rabbits's bed and the kitchen sink. The funny part was that Tigger was packing RABBIT'S stuff.
The whole show had a good number of crowning moments of funny really; one that stands out is when Christopher Robin sees a "slusher movie" and Tigger reads the title, which is basically a summary of every slasher film/series plot...
Tigger: "The Slusher Who Slushed Everyone - And Then Came Back To Slush 'Em Again!"
Heck, the entirety of the Slusher episode was a huge Funny Moment. Especially when Tigger gets on Christopher Robin's nerves.
"Un-Valentine's Day" needs mentioning here, if not the entire episode then at least...
Piglet: I AM CUUUUUUUUUPPIIIIIIIDDDDDDD!!!
The western episodes. For example, this exchange from The Good, The Bad and the Tigger:
Tigger: I am the Tigger with no name.
Pooh: I am the Pooh with a name! If only I could remember it. Oh bother.
A reminder to those who don't get it: Pooh's name is Edward Bear, except odds are almost no one who watched this knew that...
Near the beginning when Tiger is trying to get on the train and finally get's on after a considerable amount of effort. He is wondering how Pooh managed to get their so fast. Follow Pooh lampshading the event. (Which is repeated later.)
The scene in the Christmas Special when Pooh, dressed up as Santa Claus, is stuck in Tigger's chimney. Tigger thinks it's really Santa and starts bouncing gleefully around: "SANTY'S COMIN' DOWN THE CHIM-EN-Y!" It really has to be seen to be appreciated.
Not to mention Tigger "helping" Santa-Pooh get back up the chimney.
Tigger (getting a broom and fulcrum): "Hey, anything for ol'-Saint Nick! A one... a two... A FIRE!"
Catapults Pooh back up the chimney and flying far, far away.
The gang's feeble efforts to hide the fact they deflated the balloon Christopher Robin lent Pooh include Rabbit painting a boulder red (which evidently feels much heavier than the average balloon), Piglet dressing as a balloon (with his head and limbs still visible), and Tigger making a bubble gum bubble (which doesn't last very long).
From "The Wise Have It", when Piglet is trying to remember what he needs to do:
Piglet: Water the rhododendron? No... Shine the woodwork? No... Wax the floor? (slides across the floor)NoooooooOOOOOOOOO...!
"Piglet's Poohetry" is absoluty hilarious, but this line takes the cake.
Tigger: I love to smell the pritty flowers, when I take a morning stroll. But I'm so busy sniffing, I fall into a hole.
Piglet (in story):YAAAAAAAAAAAAAAAA...
This has to be Gopher's longest fall in Winnie the Pooh history, lasting well over twenty seconds.
Gopher: Muh, muh, muh, muh, mons-*gets crushed and falls back into hole* -TEEEEEEEEEERRRRRRRR...
The entirety of "Sham Pooh". Long story short, Pooh isn't hungry for honey for once, leading everyone to believe that Owl is Pooh, Gopher is Owl, Piglet is Gopher, and Rabbit is Piglet. Hilarity Ensues.