Beep-0

Beep-0 (pronounced "beep-oh") is an ally character introduced in Mario + Rabbids Kingdom Battle. It is a small robot assistant with blue "eyes" and rabbit ears, and serves to guide the playable characters throughout the levels. Beep-0 provides commentary throughout the game (with his color changing depending on its emotions), and is absent during battle sections. By default, Beep-0 does not have rabbit ears; only gaining them after entering the Mushroom Kingdom.

History
Beep-0 is first seen in the introductory cutscene of Mario + Rabbids Kingdom Battle, inside the Genius Girl's workshop as her assistant. The Genius Girl is working on the SupaMerge, a headset with the function of fusing two things together, which she hopes will solve an energy crisis. However, after experiencing an overheating problem with the headset, she leaves to take a break. Soon after, the Rabbids appear in the workshop, having been transported there by the Time Washing Machine. As the Rabbids create mischief, one of them finds the SupaMerge and puts it on. Unable to control the headset's powers, this Rabbid fuses other Rabbids with several objects in the room, creating Rabbid Peach and Rabbid Mario in the process. The Time Washing Machine is then hit by a beam from the headset, causing Beep-0 and the Rabbids to be transported to the Mushroom Kingdom.

In the sky above the Ancient Gardens, Beep-0 gains rabbit ears, while the Rabbid with the SupaMerge's headset's appearance changes as well. Beep-0 is almost hit by a falling Time Washing Machine, but is saved by Mario, who takes him to safety. Upon landing, they soon encounter Rabbid Peach and Rabbid Luigi, who join them and help them fight off a group of villainous Garden Ziggies, which they successfully do due to weapons being sent to Beep-0 by a sender called "F.B.". They later come across the Rabbid with the SupaMerge headset and Luigi. Both find a Rabbid sleeping on a Piranha Plant, and are scared by it. The SupaMerge Rabbid, as a result of the fear, unintentionally fuses the Rabbid with the Piranha Plant, creating the Pirabbid Plant. After the plant is defeated by Mario's group, Luigi joins them. They later scale a large tower of blocks and find the SupaMerge Rabbid again, scaring him. Taking advantage of the situation, Bowser Jr., who observed what happened to the Pirabbid Plant, flies in on his Junior Clown Car and befriends the Rabbid, naming him Spawny. Intending to use Spawny's powers to take over the Mushroom Kingdom while his father is on vacation, Bowser Jr. flies off, leaving Mario's group to fight Rabbid Kong. Mario's group defeat Rabbid Kong, and return to Princess Peach's Castle to report their progress to Princess Peach.

Beep-0 then joins the group as they journey to Sherbet Desert. About midway through the desert, they defeat Blizzy and Sandy, after which a recently freed Rabbid Mario joins them. They later come across the Icicle Golem and prepare to attack it, but are frozen. Just then, Peach flies in on her parasol and frees them, joining their active team as they defeat the monster.

They then travel to Spooky Trails, where they are directed by a mysterious third party (calling themselves "Tom Phan") to find the three "Relics of Goodness", which they claim have the power to defeat Bowser Jr.. After finding the three relics, they are told that a full moon is required to awaken their power. While finding a way to bring back the full moon, they encounter Calavera, holding Rabbid Yoshi hostage. After Calavera's defeat and Rabbid Yoshi's joining of the team, they venture further and encounter fortune-teller Madame Bwahstrella, who says that they are nearing their "doom". Beep-0 refuses to believe her however, not believing in superstitions. After reverting the full moon, Bowser Jr. appears with Spawny, revealing that he was sending the messages as "Tom Phan". He then scares Spawny, causing the latter to fuse a Rabbid with the three "Relics of Goodness", creating the Phantom. After the Phantom sings a song, he is defeated.