Mechawiggler appears as a giant robotic centipede with four appendages on each segment, five glowing yellow eyes, a plug for a mouth, and seven yellow lightning rods surrounding a blue plasma globe on each segment, which turn purple when calm and darken when hit. When charging, Mechawiggler turns bright orange and becomes bright with electricity; its globes cannot be damaged when doing this. While first made of nine segments, Mechawiggler increases its length to sixteen segments after taking damage.
Mechawiggler is first discovered on the top of New Donk City Hall, conducting all electricity from the entire city through the skyscraper's lightning rod. When Mario confronts it, Mechawiggler shrieks and charges him off the building down onto the streets below to engage the plumber.
Mechawiggler fights Mario by shooting electrical balls from each of its segments while crawling on the wall. To defeat it, Mario must capture a nearby Sherm and shoot at the plasma globes, causing them to darken, until all of the globes have darken, where Mario must then shoot at the motionless Mechawiggler until it squirms.
Mechawiggler then turns orange and moves faster, before phasing through the wall, obscuring it from Mario's view. Despite this, Mechawiggler's movement inside the building is marked with a spark of electricity along the outside wall, followed by a large purple portal marking Mechawiggler's point of attack. When this happens, it charges out from the vortex in a straight line at an immense speed along the ground, into another portal opposed to where it emerged. Mechawiggler continues this pattern a few times, before revealing itself outside the wall, and shoots four electric spheres. After this, it calms down, and its globes relight, now a pink color. Mario must again destroy the plasma globes while avoiding the beams. However, now Mechawiggler can possibly become angry before Mario finishes, and makes a single charge across the ground, before climbing onto another wall, where it calms down after shooting more electricity, allowing Mario to continue. Once all the globes have been hit again, Mario must attack Mechawiggler in rapid succession yet again until it is defeated.
Once defeated, Mechawiggler shrieks one last time before exploding from head to tail in static burst, releasing a Multi-Moon. All that remains of Mechawiggler is its head that crashed in Mayor Pauline Commemorative Park, which releases a Power Moon if Ground Pounded. A bystander nearby comments how observing the ruined remains made him feel sorry for the thing, only just a little.
Although Mechawiggler was destroyed, Bowser stole enough electricity through the Broodals and Mechawiggler to stabilize his wedding church built on the Moon.
In the Mushroom Kingdom rematch, Mechawiggler is the most different of the six re-fightable bosses. As such, it is able to split itself in half and launch pink electrical orbs that split in multiple bursts.
- Although Mechawiggler's name links a similarity to a Wiggler, it bears little to no resemblance to them. While Wigglers are based on caterpillars with two legs on each segment, Mechawiggler resembles a centipede with four appendages on each segment, plus it has a more insectoid face compared to the cartoonish nose, eyes, and smile of regular Wigglers. Although Mechawiggler does have a similar enraged state compared to Wigglers.
- Mechawiggler is one of the only three bosses in the game that is defeated in more or less than three hits, sharing two hits with the first battle against Topper in the Cap Kingdom. The other is the Robobrood, which takes four hits.
- Mechawiggler is one of the two bosses of Super Mario Odyssey who conducts electricity, the other being the Ruined Dragon.