The increasingly absurd Stock Footage representing the army attacking the monsters. To quote the trope page: "planes taking off, tanks driving away, navy vessels sailing on the sea, cavalry riding across the screen, sumo warriors struggling, baby turtles running across the beach, and Zulu warriors cheering. In that order." In a Brick Joke, the Zulu warriors are seen cheering again when the narrator announces that the Big Bad has been defeated.
In "Up All Night", Daggett tries to do a prank call. Not only does he botch the punch line, but Norb sets him up to call their mother:
Daggett: Hey, chicken-neck, you should wear a sweater!
Mom: Dagget, is that you?
Everything in that episode is genius. From "Eat ball, ratface!" to Norb and Dag collapsing into hysterical laughter over thinking the monster from "The Crawling Spleen" was in their house, to the end of "Dag...how long have we been awake?!" is gold.
The entirety of "Three Dag Night". Cloning yourself has never been so hilariously fun!
All of The Big Frog, where after Norbert snaps at Dagget to grow up and stop playing with his baby bunny dolls yest he'll embarrass them. Strangely, Dagget shrugs and complies... and the next scene has him acting like a Bumbling Dad, with over-the-top clothing trends (such as many reading glasses and pants tied up above his waist) and doing all sorts of 'mature adult' things like getting Norb to eat his stew instead of chips (healthy food), swinging his golf-club to work while saying any number but 'four' as he leaves, and literally 'bringing home the bacon'. It's breaking down Norb's normally cool and collected persona... and WORKING.
And much later, Norb starts regressing to a childlike state and playing with Dag's bunny dolls, to which Dag joins in and pretty much states he was doing the whole thing on purpose just to mess with Norb.
"There's an alien invasion in the bathroom!"
Dag's "hook" persona in Things That Go Hook In The Night. With such tidbits as "Not sharp enough! NOT SHARP ENOUGH! Try it on him! You'll see! YOU'LL SEE!" And:
Dag/"Hook": Sing with us! Sing with us, silly beaver! Sing "The Happy Hook Song!"
Daggett: I sure wish I'd gotten around to training him, though.
The episode "Up All Night 2: Up All Day: The Reckoning". It perfectly squeezes the sense of your brain stopping to work properly when you're tired and creates a short animated episode full of ingeniously absurd dialogue out of it.
Every appearance of (Dag dressed up as) Muscular Beaver, and the sheer havoc it brings. His apparent superpowers and gadgets are downright wacky even for a superhero, and Dag's representations of them become simply uproarious, from the Cloak of Limited Visibility (conveyed by Dag pretending to hold it up and make "vveeerrreerreerr" noises) to his Razor-Sharp Wondrous...FUR OF STEEL! (one extra-long hair sticking out from his chest). Dag singing heroic music as he "flies" around tops it off perfectly.
The later half of Chocolate Up To Experience where Dag is forced to sell a single chocolate bar for $200 all the while Norb gorges himself on a warehouse full of chocolate. As Dag receives physical injuries Norb sends him Ice-Cream Koan messages about being a good salesman, until Dag finally gets fed up after receiving one about quilting that makes no sense at all. When Dag actually does make enough money, he asks this about when he's going to get his quilt. Norb asks if he'll accept steak knives.
Norbert's ridiculous inspirational speech in "The Loogie Hawk":
Norbert: Think of your poor old mother wearing Bologna shoes and corrective headgear. She thinks small animals nest in boxes of tapioca left under the yum-yum trees for too long, but that's the way she was raised! Rub that on your thighs, Mr. Melto, and see how far it gets you! How do you like them apples?!
In Fish and Dips, Daggett's attempts at capturing the legendary "Old Gramps" include a diving cage. Which drops to sink only as deep as his waist before hitting bottom in a shallow part of the lake.
Norbert: (snickering) "Oh, this one's for the refrigerator." (snaps photo)
That moment in "Dumb Waiters" when Dag seemed to have been seducing Muffy Snootwell while playing the violin, and her husband won't be having none of that.