Mecha Jr.

Mecha Jr. is the midboss of the Lava Pits in Mario + Rabbids Kingdom Battle. As its name suggests, it is a mecha operated by Bowser Jr., resembling a large robotic Rabbid. It has long, relatively thin limbs supporting its cylindrical body; the feet have rocket boosters and the arms end in pincers. It is armed with a massive hammer with a head resembling a cow. It also has a compartment in its chest, used to store Spawny and deploy mobile bombs during the battle.

Mecha Jr.'s behavior is similar to that of a Smasher; it charges at the heroes in an attempt to smash them with its hammer. Like a Smasher, it moves prematurely towards its attacker when attacked at range; unlike a Smasher, it is immune to movement-based attacks such as Dashes and Team Jumps. It has two additional abilities: a variation of Magnet Dance to draw characters towards it, and mobile bombs (similar to Luigi and Rabbid Peach's secondary weapons) that also head towards the heroes. A pair of Valkyries are present to support Mecha Jr.

When Mecha Jr. is defeated, it malfunctions and bops itself on the "head" with its own hammer. Bowser Jr. narrowly escapes his mech's destruction, but drops Spawny in the process as he flees from the heroes. Luckily, Yoshi rescues Spawny, and both join the group.

Trivia

 * Mecha Jr.'s subtitle is "Jr's Fave B-Day Gift!"
 * A diagram of, what appears to be Mecha Jr. (albeit with a slightly different appearance), can be seen on a chalkboard in the background of the battle arena.