B.O.B. and his monstrous crew are on a mission to bust out of the government’s top-secret holding cell. Led by mad-scientist Dr. Cockroach Ph.D and macho amphibian The Missing Link, the trio outwits grizzled General W.R. Monger to make a triumphant escape ... almost.

Susan Murphy (a.k.a. Ginormica) and the Monsters are now working with the US government as special ops. So when an alien presence is detected in Susan's hometown of Modesto, California -- right before Halloween -- the team is dispatched to investigate. Everything appears normal, right down to the jack-o-lanterns peering out from every doorstep and windowsill. But when Halloween arrives, those innocent-looking carved pumpkins reveal themselves for what they really are mutant aliens. The altered pumpkins then start to implement their fiendish plan to take over Earth. The Monsters are there to combat the mutant gourds and try to smash their wicked scheme!

After a mutant alien pumpkin explodes on the Murphy's carrot garden, zombie carrots start attacking the immediate area, and it's up to the Monsters to save the night again.

All is well at Area Fifty-Something with Team Monster, until a lone alien imprisons the President and makes a permanent home on base.

The president's birthday is here! Dr. Cockroach has made him a gadget that will make him appear younger, but instead blasts him to infanthood.

The Monsters snoop in Coverton's quarters, where they find his "cuddle bear", which then attacks everyone on B.O.B.'s commands.

Susan makes B.O.B. think that baths cure crankiness - B.O.B. leaps into action, chasing after Coverton to cure his crankiness once and for all.

When Link accidentally eats the gelatin that B.O.B. calls his "girlfriend", it's up to the gang to figure out how to break the bad news.

B.O.B. is determined to have Coverton be his emergency buddy. Instead, Coverton chooses to manipulate B.O.B. to help him steal a death ray.

Impressed with B.O.B.'s indestructibleness, Coverton decides to clone a piece of him. After too many clones, B.O.B. alarmingly begins to diminish little by little.

The Monsters find an alien called Sqweep in the woods doing an earth studies project, which has a lot of sensitive data that could be used for an invasion.

It's all fun and games when Link and B.O.B. use Sqweep's tablet TV as a raygun, until a doomsday app is initiated that could destroy the planet.

B.O.B. discovers a secret switch that General Monger tells him not to touch. Will it get rewired before the Big Blue Blob can get to flip it?

Dr. Cockroach overpromises that he's made a teleportation machine. Instead he's made a short wormhole and tries to pass it off as the real thing.

Dr. Cockroach is split into two personalities by his new teleportation machine.

Coverton installs an "evil" switch in a brain that Dr. Cockroach builds for B.O.B.

Sqweep accidentally gives everyone except for B.O.B. the brains of a dog when he wants to do research on puppies.

Sqweep creates a memory extractor which releases a monster from a scary movie.

To get strong enough to pass an obstacle course, Dr. Cockroach tweaks his 50/50 man/roach genetic makeup so he'll be 40 percent man and 60 percent roach. Unfortunately, his roach side keeps increasing at the cost of his human side and its intellect, forcing his teammates to find a way to reverse the process.

General Monger takes Susan, B.O.B. and Sqweep on a camping trip to the desert. But when a lightning storm destroys their supplies and Monger is injured, Susan must take charge to get them back to base.

When a vicious alien beast known as a Vornicarn hatches on Earth, the alien huntress Sta'abi arrives searching for it.

Susan tries to prevent the monsters from destroying the base with a doomsday prank.

Dr. C's former teacher reveals a missing music grade in his transcript.

Susan accidentally gets Sta'abi hunting for her after learning that apologies are a mark of disgrace for her people.

After the monsters are informed that uttering alien swear words result in physical consequences, Coverton passes a list of those words B.O.B. to cause havoc.

Coverton plans to use Dr. C's invention to hack the base's mainframe.

Monger puts Sqweep in time out for making a mess.

The monsters hack into Monger's top secret files.

Monger orders the monsters to clean up the Rec Room.

Sqweep has to go "number seven."

Link pursues Sta'abi using a pheromone spray.

Link and Sta'abi duel for driving privileges of a new car.

When an asteroid is detected heading for Earth, Team Alien is put in charge of the rocket being sent to destroy it. Meanwhile, Dr. C sends B.O.B. to play hide and seek. Unfortunately, he winds up hiding in the fuel being used to power the rocket, and Team Monster must rescue B.O.B. and alter the rocket's trajectory so it'll actually hit its target.

Coverton tries to steal base secrets when everyone gets the alien flu.

Vornicarn's bad behavior lands him in the Isolation Zone.

B.O.B. eats Dr. C's ``probabilitator'' and foresees Coverton with a crown.

Sta'abi is summoned to embark on her Warrior Vision Quest.

Dr. Cutter arrives to update the base's technology.

Link and Bob fix up an old spaceship and take it for a joyride.

A stray kitten makes its way to the base and obtains Susan's ginormica powers.

Sta'abi recruits Bob to teach her the art of combat.

When Derek returns, strange secrets begin to unfold.

The monsters and the aliens are introduced to Rule-Bot when Monger goes away for the weekend.

Monger gathers everyone for a game of dodge ball.

Dr. Cockroach creates a spray to give the president more authority.

The monsters begin to borrow from Sqweep's allowance.

After Dr. C tampers with Sqweep's project, the alien receives a bad grade.

Dr. Cockroach accidentally teleports the diner into space.

Link is disappointed when he can not play in the government football game.

A leprechaun joins team Monster.

After seeing something horrifying in Coverton's room, Team Monster must submit to memory wipes.

Susan tries to escape the Internet.

A metal robot battles with the monsters and aliens.