Rodent Ruckus is a Rocket Barrel level in a mine made of cheese. This level has plenty of these moments, from the mouse enemies excavating it like treasure, to the finale, where you have to maneuver behind, in front, and inside a giant wheel of cheese. It's as ridiculous and awesome as it sounds.
The end of Reckless Ride. For context, it's a rocket barrel level where a penguin in a wooden robot will attempt to attack you constantly during the stage. At the end, the robot is smashed upon colliding with a barrier and the penguin goes flying. Wait a moment before hitting the end of level barrel and you'll see the penguin land in the background, only to get eaten by a carnivorous plant.
At around the middle point in Blurry Flurry, players will see a very familiargiant battrapped in ice. Funnier still (or slightly terrifying depending on how you look at it) is that you can hear him yell for help and watch as his eyes follow you.
Everything about Cranky Kong. The fact that you can play as him at all, his animations and sound effects, his versions of the end-of-boss-battle pummelings, and his ground-pound animation. Even better is Hard Mode, where you're restricted to one Kong but can play as Kongs other than Donkey. You can solo the whole game in Hard Mode as Cranky Kong if you so desire, which is hilarious whether you succeed or fail.
DK's partners get to use weapons. Diddy's is the classic Peanut Popgun, Dixie's shoots bubble gum, and what does Cranky's gun fire? Dentures.
In the the intro cutscene before the battle, Bashmaster is relaxing on a ice float, licking a Popsicle, only for DK and/or another Kong to slide out of a chute and land on the platform, knocking the Popsicle out of his hands and into the water, where it's eaten by piranhas. This prompts Bashmaster to angrily turn on DK and/or another Kong, who put(s) on a hilarious guilty smile. If Funky does this, he'll just cross his arms and shrug as if to say "hey, shit happens."
During the fight, every time you hit him, he stumbles backwards into the purple liquid surrounding the battle area. As the fight goes on, you'll notice that his fur slowly gains a purple tinge - it's getting stained by the water!
In the Wii U version, DK has an Idle Animation where he pulls out a 3DS and plays it. It doesn't change much when he has a partner on his back (Diddy watches him play, Dixie grooms DK as he plays, and Cranky reads a newspaper). Fast-forward to the Switch version where in addition to the 3DS animations, there's another set that are similar, except DK is playing a Switch this time. Not only that, the animations that play when DK is with his partners change dramatically:
DK takes the Switch out, detaches the Joy-Con, gives one to Diddy and they play a game together. Diddy gets a bit excited and repositions himself so that his Joy-Con is in front of DK's eyes, much to the latter's annoyance.
DK prepares to play a game by himself, only for Dixie to snatch both Joy-Con from the system and play the game on her own. Unamused, DK just holds the Switch itself for a moment before offering it to Dixie. The latter then sheepishly puts the Joy-Con back onto the console.
DK plays the Switch while Cranky reads a newspaper, just like the 3DS idle. Except this time, DK offers a Joy-Con to Cranky. Cranky refuses, goes back to his newspaper, then smacks his grandson upon his head with it so they can get back to adventuring.
In the Switch version, Funky reacts spectacularly to Skowl smashing a banana to a pulp.
Dixie's helicopter hair is strong enough to not just lift Donkey Kong, but Rambi the Rhino as well!
When Lord Fredrik is in the background, you'll have to pick up an enemy he sends at you and toss them back at him to make him leap back to the foreground. However, if you barely miss, he'll respond by doing a little dance for a second, sometimes like a ballerina.
in which Donkey Kong attempts to fight some penguins..... and fails spectacularly.