Kazooie

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

Kazooie, like Banjo, is owned by Rare Ltd., a former second-party developer for Nintendo. In 2002, Rare was sold to, and the rights of both Banjo and Kazooie were transferred to the company.

Diddy Kong Racing
Although Kazooie is absent from Diddy Kong Racing, she is mentioned in the instruction manual, interestingly before she ever debuted in a video game.

N-Gang
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. Mario referees the match.

Super Smash Bros. Ultimate
The Super Smash Bros. Ultimate reveal trailer for the duo was shown off during a Nintendo Direct on June 11th, 2019, releasing sometime in Fall 2019. The reveal trailer heavily references King K. Rool's original reveal trailer, with Donkey Kong, Diddy Kong and King K. Rool looking outside a tree house window and seeing a silhouette of Banjo-Kazooie. It is then revealed to be Duck Hunt playing a prank, much like the K. Rool reveal trailer had King Dedede pretending to be King K. Rool. Banjo and Kazooie then appear from the sky, and knock Duck Hunt out of frame, with Banjo holding his signature instrument he is named after, the banjo. The trailer references Banjo's heavy connection and roots to the Donkey Kong franchise as both were owned by Rareware (now called Rare Ltd.) in the 1990s, and Banjo's first appearance was in Diddy Kong Racing.

Their moveset and appearance is directly pulled from their two Nintendo 64 titles, Banjo-Kazooie and . Spiral Mountain, the location of their home, serves as the representation for their stage.

Super Smash Bros. Ultimate marks their first appearance on a Nintendo system since 2005's Banjo-Pilot for the Game Boy Advance, and their first physical appearance in a new game since the Xbox 360 version of 2010's Sonic & Sega All-Stars Racing. This is Kazooie's first appearance alongside Mario characters in a video game.