Banjo is a laid-back, well-mannered brown bear who loves honey and, as his name suggests, playing his banjo. He is generally non-confrontational, desiring peace and quiet, and he often helps those in need, but he is strong enough to defend himself if need be. He is a foil to Kazooie, his best friend whom he (often unwittingly) goes on adventures with. He lives with Kazooie and his younger sister Tooty in a small house near the foot of Spiral Mountain.
Banjo chronologically first appeared in Diddy Kong Racing as one of the eight starter characters. He is the second-heaviest character, and races in aqua-colored vehicles. Kazooie does not appear, but is mentioned within the game's instruction manual.
His first proper adventure, however, occurred in Banjo-Kazooie. The evil witch Gruntilda, upon hearing that Tooty is the prettiest girl of all, kidnaps her and attempts to use a machine to steal her youth and beauty. Banjo oversleeps while this is happening, but soon awakens and begins his journey to rescue his sister. With the help of Bottles, the move-teaching mole, Banjo and Kazooie navigate through Grunty's Lair, a complex cavern across Spiral Mountain with links to many disparate worlds. Throughout the lair, Banjo acts as mostly a platform for Kazooie's attack and movement abilities; he himself does little more than run, swim underwater, and talk to the various inhabitants of each world. The friendly shaman Mumbo Jumbo also transforms Banjo into various creatures and objects, allowing him to bypass certain obstacles. After the pair get through the lair and confront Grunty at its peak, they ultimately summon the Jinjonator to push her off the tower to her doom; she crashes into the ground and is buried by the ensuing debris.
Two months later in Grunty's Revenge, Grunty's ogre-like minion Klungo creates a robotic body for her spirit to possess while her body remains underground. This newly-built "Mecha-Grunty" kidnaps Kazooie and travels 20 years into the past to stop the two from meeting, thus preventing her defeat. Mumbo uses his magic to send Banjo back in time and stop her. Banjo is necessarily more of an independent character in this adventure, able to defend himself alone until he manages to rescue Kazooie. The duo eventually send Grunty's spirit back to the future into her real body, restoring the timeline back to normal.
Two years later in Banjo-Tooie, Grunty's sisters appear to rescue the now-skeletal witch, who promptly attacks Banjo's house and kills Bottles. Banjo and Kazooie set out again to chase down the witches, who are attempting to restore Grunty's flesh by using a Big-O-Blaster to suck the life out of the entire Isle O' Hags. Bottles' brother Jamjars helps the duo learn to work independently, giving Banjo several Kazooie-free moves that utilize his backpack to attack, relocate unwilling cargo, sleep to regain energy, and protect him from dangerous liquids. Banjo and Kazooie triumph over Grunty once again, and use the B.O.B. to revive Bottles.
Eight years later in Nuts & Bolts, the duo has become lazy and out of shape from their lack of exercise, having forgotten their moves from the previous games. Grunty reappears as just a skull and attempts to start a fight, but before they can, they are interrupted by the Lord of Games (L.O.G.), supposedly the creator of all video games. He creates a robotic body for Grunty and a series of vehicular challenges for Banjo and Kazooie to go through. Banjo acts as the driver for all vehicles and can train at Boggy's Gym to improve his physical attributes, though with the game being vehicle-based, this is of dubious usefulness. The pair eventually battle and defeat Grunty, who is forced to work in L.O.G.'s video game factory, and earn back their old moves.
As a playable character
Main article: Banjo & Kazooie (SSBU)
Banjo and Kazooie were announced as playable fighters, alongside the Hero, during the E3 2019 Nintendo Direct on June 11, 2019. As always, Banjo himself is the primary face of the duo, handling basic movement and weak attacks.
According to Masahiro Sakurai, Banjo & Kazooie were heavily requested characters for a long time even leading up to Ultimate's launch, particularly in the West. Even after character reveals like Ridley and King K. Rool, requests for Banjo & Kazooie still kept coming in. While their inclusion would have been a natural one in the past, they were sold to Microsoft soon after, and it was originally thought that Nintendo shouldn't collaborate with their console competitors. However, thanks to Rare and Microsoft's cooperation, the rights to the characters were easily secured, as Microsoft had developed a strong third-party relationship with Nintendo leading up to their Smash reveal.
In their gameplay showcase on September 4th, 2019, Sakurai openly acknowledges the fact that the intellectual property is completely owned by Microsoft. He also acknowledges Rare and Microsoft's cooperation in bringing the franchise into Super Smash Bros. Ultimate, as they were happy to see the duo in the game and saying Rare welcomed Nintendo with open arms. He even notes that if those interested in the series want to play the original titles today, they should do so in Rare Replay on the Xbox One.