Spawny is a Rabbid who appears in Mario + Rabbids Kingdom Battle. In the Mushroom Kingdom, he is differentiated from other Rabbids by his white snout, blue belly and ears, the fused SupaMerge headset that covers his eyes and the on / off button on the lower back. His ability is to blow other beings with Rabbids, thus doing to create the Pirabbid plant; however, this power is uncontrollable and is activated whenever it is stressed.
His name is given to him by Bowser Jr., who seeks to use his powers to take over the Mushroom Kingdom. Although he is a great catalyst for the game's events and forms an alliance with Bowser Jr., Spawny is not evil.
Spawny begins as an ordinary Rabbid, but when he and many other Rabbids are transported to the Genius Girl's laboratory, Spawny steals SupaMerge and uses it to fuse other Rabbids with objects, thus creating Rabbid Peach and Rabbid Mario. When Spawny enters the Mushroom Kingdom, SupaMerge ends up interacting with him, transforming him into his appearance throughout the game.
Beep-0 informs Mario that SupaMerge has been corrupted upon entering the Mushroom Kingdom, and he agrees to find Spawny. However, just like Mario and co. are about to pick up Spawny in a tower overlooking Old Gardens, Bowser Jr. appears and befriends Spawny. Mario and co. Traverse the other three worlds and eventually defeat Bowser Jr. in his mech, Mecha Jr., retrieving Spawny in the process. However, the portal on the Mushroom Kingdom releases a dragon named Megabug, who captures Spawny and harnesses his power to liberate more beings. Mario and co. end up defeating Megabug and freeing Spawny and Bowser (which was also corrupted by Megabug). Spawny is then seen in the pre-credits scene, where he admires the statue erected in honor of Rabbid Peach. Spawny appears with Bowser Jr. at the beginning of Donkey Kong Adventure,where he shoots a Lightning Ray on the Wash Machine after Rabbid Kong enters, causing him to close.
When he is still an ordinary Rabbid, Spawny is mischievous, curious and playful as his fellow Rabbids, while always causing trouble without thinking of the consequences. After his transformation, Spawny becomes shy, naive and childish. This makes Bowser Jr. take advantage of him by intimidating him to use his skills. Since his power comes from fear and stress, Spawny has little or no control of his abilities.
Bowser Jr.: Upon seeing Spawny's abilities, Jr. decides to use Spawny for his personal gain in order to defeat Mario and co, and make his father proud. After giving him his name, Jr. attacks the naïve personality of Spawny to make friends with him. Little Rabbid soon discovers that Bowser Jr. is only using him and makes several attempts to get away from him. Despite all this, Bowser Jr. usually worries about Spawny, showing concern when he falls out of his clown car and even rebukes Mario et al. when he is kidnapped by Megabug. After Spawny is safe, thanks to Mario and his colleague, Jr. gives it to the heroes, relieved that the young Rabbid is safe.
Mario, Luigi, Princess Peach and Yoshi: Due to being dominated by their power, Spawny becomes uncomfortable with Mario and friends, fearing that they are his enemies. Spawny is surprised when he and Luigi wake up a Piranha Plant, and that scares him, causing him to create the Pirabida Power Plant. Throughout the game, Spawny becomes restless with the heroes, causing more stress, but ends up realizing that they want to help. After the battle with Mecha Jr.Spawny falls from the clown car and is saved by Yoshi. After being rescued from the Megabug, Spawny eventually becomes friends with the group and sets up. He seems to be closest to Princess Peach as his trophy shows her holding him while he smiles, and she holds him up during the opening of the statue of Rabbid Peach. In a work of art, Spawny is giving the princess a holographic mustache to her surprise.
Rabbid Mario, Rabbid Luigi, Rabbid Peach, Rabbid Yoshi and Rabbids: Prior to his transformation, Spawny treats his fellow Rabbids with compassion and malice. After his transformation, he becomes shy and timid around them, possibly from the stress of his new powers, trying to avoid them from hurting them. With the heroic Rabbids, he is afraid of them because he thinks they are his enemies but ends up warming up to see them as friends.
The Spawny mask should be a reference to the Studio Ghibli movie, Castle in the Sky .