Kazooie

Kazooie is one of the main characters from the Banjo-Kazooie franchise, first appearing in Banjo-Kazooie for the Nintendo 64, where she serves as Banjo's partner. As a playable duo, Banjo and Kazooie appear together in Super Smash Bros. Ultimate as the third Fighters Pass DLC character. She belongs to a fictional species of birds called the Breegull.

Diddy Kong Racing
Although Kazooie is absent from Diddy Kong Racing, she is mentioned in the instruction manual and official Nintendo Player's Guide, prior to her debut in a video game. An additional nod to her is featured in the form of a kazoo being played during Banjo's segment of the opening title sequence, though it is absent from Banjo's theme on the character select screen. This segment is still included in the remake, Diddy Kong Racing DS, for which Banjo did not return for.

Donkey Kong 64
Both Banjo and Kazooie made a cameo in early versions of Donkey Kong 64, but were ultimately cut from the final game. Their faces were going to appear on a shower stall in DK's Tree House.

"Freeze Frame"
Banjo and Kazooie make a brief cameo at the end of the N-Gang comic "Freeze Frame", where they are seen celebrating alongside other Nintendo characters.

"N-Gang vs. Nintendo"
Kazooie appears alongside Banjo in the 2000 N-Gang comic "N-Gang vs. Nintendo", where they play on the same soccer camp team with Wario, Yoshi, Princess Peach, Donkey Kong, and Lanky Kong.

"Die Hexe lacht um Mitternacht"
Kazooie makes a brief cameo at the end of the N-Gang comic "Die Hexe lacht um Mitternacht", where she is seen at a Christmas party with other Nintendo characters.

Mario Artist: Paint Studio
Artworks for Kazooie, along with Banjo and other Banjo-Kazooie characters, make an appearance in Mario Artist: Paint Studio.

Minecraft
On January 30, 2018, both the Wii U and Nintendo Switch versions of Minecraft received an update that included many Microsoft-related character skins, including Banjo-Kazooie characters like Banjo and Kazooie. This is the first time Kazooie appears with Mario characters in a game.

Super Smash Bros. Ultimate
Kazooie, alongside Banjo, were announced as playable fighters in Super Smash Bros. Ultimate during the E3 2019 Nintendo Direct on June 11 (PST). Ultimate marks their first non-cameo appearance in a new game since Sonic & Sega All-Stars Racing with Banjo-Kazooie, which was released for the in 2010, as well as the duo's first appearance on a Nintendo console since Banjo-Pilot. Banjo & Kazooie were released on September 4, 2019 (PST) as part of Challenger Pack 3.

In the duo's reveal trailer, a Jiggy bounces across the floor as Donkey Kong, Diddy Kong, and King K. Rool are lounging in Donkey Kong's tree house, causing them to look outside the window and seeing a silhouette of Banjo & Kazooie. It is then revealed to be Duck Hunt playing a prank, in the same manner as King Dedede pretending to be K. Rool in the latter's reveal trailer. Banjo & Kazooie then appear from the sky, knocking Duck Hunt out of frame, with Kazooie holding her namesake instrument, the kazoo. Kazooie and Banjo appear in Sephiroth's reveal trailer, and are shocked to see him descend from the sky.

Banjo & Kazooie's moveset and appearances are directly pulled from their two Nintendo 64 titles, Banjo-Kazooie and , though they also sport a few original attacks. Spiral Mountain, the location of their home, serves as the representation for their stage. Regarding weight, Banjo & Kazooie are a heavyweight fighter, being heavier than Link, Yoshi, Captain Falcon, and Mii Gunner, but lighter than Wario, Ike, Ridley, Simon, and Richter, while having the same weight as Snake and R.O.B..

When Kirby copies Banjo & Kazooie, his backpack has a plush toy version of Kazooie inside.

Palutena's Guidance
Banjo and Kazooie shares this stock conversation with all other DLC characters except Piranha Plant. It was originally used for Mewtwo, Lucas, Roy, Ryu, Cloud, Corrin, and Bayonetta in Super Smash Bros. for Wii U, who are downloadable fighters in that game.
 * Pit: Who is THAT?
 * Palutena: I have no data on this fighter. I can't believe it!
 * Viridi: It must be an intruder from another dimension!
 * Pit: Whoever it is, the goal remains the same: to fight and win!

Official website

 * The missing piece of the puzzle is found as Banjo & Kazooie join Super Smash Bros. Ultimate as a playable fighter! With Banjo’s bare hands to bruise rivals up close and Kazooie’s egg-cellent shooting skills, your rivals will be singing the blues in no time. For their Final Smash, these perfect partners call upon a flock of Jinjos and the Mighty Jinjonator to deal the final blow to any “feeble jerk” that may stand in their way!

Trivia

 * Prior to Banjo and Kazooie's inclusions in Super Smash Bros. Ultimate, they were among the most requested Super Smash Bros. characters of all time. A Rare employee wrote on their website back in 2009, that although they hadn't been considered for Super Smash Bros., many Rare franchise trophies were originally in Super Smash Bros. Melee. Vice President of Microsoft's gaming division,, made a Tweet in 2015, stating "it would be cool" to see Banjo and Kazooie appear as DLC fighters in Super Smash Bros. for Nintendo 3DS / Wii U. He doubled down on the comments in 2018, a year before Banjo and Kazooie's reveal in Super Smash Bros. Ultimate.