When Melissa’s dad drives her and Milo into town on a decommissioned old fire engine, chaos ensues.

Milo and Melissa finally tell Zack the story of the infamous Llama Incident.

When Cavendish and Dakota stop Milo from destroying a pistachio plant, they change the future. Pistachio plants become sentient and take over the planet, so Cavendish, Dakota and Milo must race through time to save the future.

Elliot Decker is hired as the school’s head safety monitor.

Milo, Zack and Melissa set out in search of a missing robot that previously escaped.

Milo begins to sleepwalk through some nearby woods. Meanwhile, Cavendish and Dakota have a "ditch day" from pistachio duties after their ordeal with the Pistachions.

The students take a trip on the school yacht.

Parents become children at Back to School Night.

Elliot gets to see what the world would be like without Milo.

Milo runs a race as Cavendish and Dakota gets stuck in the Old West.

With Milo away skiing, Sara finally feels safe enough to go on a date.

Dakota travels back in time to save Cavendish.

Milo, Cavendish, and Dakota travel back to 1965 and inspire the creation of Dr. Zone only to encounter a sinister plot to take over the world.

Zack doesn’t think anything about Halloween can scare him anymore, but he didn’t account for Murphy’s Law.

Milo surprises his parents by inviting the extended Murphy family to town for Christmas, multiplying the effects of Murphy’s Law.

While waiting for Milo to come join them for lunch, Melissa, Zack, Bradley, Mort, Chad, and Sara present "Neil From the Comic Shop" with differing theories on what Milo really is; ranging from him being a wizard, a supervillain, and a robot.

Milo gets abducted by the recurring alien characters introduced this season, while Melissa, Zack, and Doof attempt to look for him. While on trash duty, Cavendish sees the abduction from a distance, but Dakota does not. This causes a large argument between them, which ultimately ends in the dissolution of their partnership and the former going rogue.

Eons in the future, an elderly man tells his grandson how a sentient crockpot of goulash came to be and defeated an army of robot screech owls. Back in the past, Milo, his friends, and Doof attempt to protect Brigette's goulash from Murphy's Law and Doof's hand-held-inators.

After being told to go home again, Diogee crosses paths with Agent P and enemy agents after he swallows a flash drive disguised as a cookie. Meanwhile, Brigette makes Doof and Sara pick up dirty clothes, so the former builds a robot hamper-inator to do the job for them.

Doof becomes inspired to find an "adventure buddy" to get over Agent P, and winds up joining Scott on a boat ride through the sewers.

While attending a school award ceremony, Milo attempts to get to the stage in time to collect an award he was nominated for. Meanwhile, Diogee ends up riding along with two of Danville's police officers while they attempt to catch Zippy, the world's fastest koala, and rescue one of their K-9 officers.

Milo attempts to escape his room so he can go out for the day with Zack and Melissa. Elsewhere, Dakota teams up with Doof to find Cavendish, who's attempting to show various news outlets a crashed U.F.O. with a malfunctioning cloaking device.

After Zack breaks his leg getting tangled in a harp while doing interpretive dance, all of his friends plan a "cast party". At said party, everyone shares stories of how they all broke something without Milo, Martin, or Murphy's Law around; as far as they know.

Milo and Elliot accidentally get handcuffed together. Meanwhile, Zack and Melissa attempt to make a student film, but Doof messes everything up.

Milo, Zack, and Melissa attend a camp to learn new skills. Elsewhere, Cavendish mistakenly unleashes a giant alien.