The Banjo-Kazooie series as a whole is hilarious, but one of this troper's favorite bits comes from Tooie. A really freaky character named Canary Mary can be raced for a Jiggy—she tells you it's been wedged under her wing. When you beat her again and she gives you a Cheato page, this exchange takes place...
Canary Mary: Oh, thank goodness! Here, you can have this. It's been wedged under my...
Kazooie: NO! We don't want to know where it's been!
Kazooie is a never-ending stream of this in Tooie, due mostly to her role as the Meta Girl and having her Deadpan Snarker tendencies increased by at least a magnitude.
Her exchanges with Salty Joe in Witchyworld.
Joe: Looks like I'm outta fries. I'd better whip up some more. Kazooie: Yeah, you should prepare for the impending rush. Joe: Why, you cheeky little...
Then there's Lord Woo Fak Fak's pre battle dialogue in Tooie:
Lord Woo Fak Fak: You were going to steal my jiggy and drain my home, leaving me to flap pathetically around on the bottom until I shriveled up and died. Weren't you?
Kazooie: Something like that.
Gruntilda's rhymes will forever be stuck in my head.
Repeating over and over until you're dead?
In the first level of Tooie, when you retrieve the MacGuffin for the guy, he was about to cuss when Banjo interrupts him with, "This is a family game!"
In Tooie, whenever you get the secret unlockable attack that involves grabbing Kazooie out of the backpack and BEATING ENEMIES WITH HER. Every player first laughs, then feels terrible...then laughs some more.
Gruntilda's full name. That is all.
Grunty: "...and you'll wish you'd never messed with the great Gruntilda Winkybunion!"
Kazooie: "Your last name's Winkybunion?"
Grunty: "Erm... no it's not. And if you tell anyone, I'll kill you!"
Banjo: "Sure thing, Winky."
Could count as a Crowning Moment of Awesome for Banjo, as it's one of the rare times he of all characters snarks like Kazooie.
Nuts And Bolts is by far the most self-aware installment in the series, constantly pointing out the poor logic of the game's universe. Some examples;
Cleaning up the debris after the volcano erupts causes Humba to say "Good thing I had this Jiggy to give away as a reward in case a random emergency happened!"
The level introductions are parodies of 80's sitcoms, complete with their theme music. For some reason, people over 30 find this hilarious.
Gruntilda admits to Banjo that if he beats her in a race she won't go through with her latest evil plan ( Polluting the water by having her cat take a crap in it) Kazooie points out how stupid this is, while Banjo claims it reminds him of something he did a long time ago "...and there was a genie and a giant pig."
Description for Spirit of Pants: Rubbish Rare website mascot now rubbish vehicle mascot. Not exactly flying lady like on sophisticated cars.
Description for Papery Pal: Bear put papery critter on vehicle and be filled with fun. Mumbo like 'Trouble in Paradise', recommend player buy it tomorrow.
In Banjoland, a museum made up of elements from past games, the giant trash can appears, literally filled to the brim with copies of Grabbed by the Ghoulies boxes.
Boggy appearing twice in one act, lampshaded by both Banjo and Kazooie.
If you lose to the Final Boss in Tooie and try again:
Grunty: Back for more, eh? Banjo: Just shut that hatch, and let's get on with it. Grunty: Fair enough.
In the beginning of Banjo-Kazooie, Banjo sleeps through his sister's kidnapping, with his backpack, Kazooie included, hanging on a hat stand. Eventually, Kazooie gets fed up and shouts at Banjo, rocking the stand so much it falls over!
In the beginning of Banjo-Tooie, Bottles is killed when Gruntilda blasts Banjo's house during a poker game. (He didn't evac because the whole 'Grunty's back!' thing was just a gag) When Banjo and Kazooie meet Jamjars and relate the sarge about his brother's untimely demise, Jamjars asks if Bottles went down fighting.