One day, two groundskeepers of a nearby park named Mordecai and Rigby made their way to the farm after hearing about a cow that farmer Bob have imported from Asia. The two were supposed to be cleaning the park after they threw a party which quickly grew out of control the other night when Benson was at the anger management seminar, needless to say it didn't end well after another apocalyptic disaster triggered by Rigby when he stumbled upon three giant red trucks that combines to form a mecha. It was due to a help from their coworker, Skips thanks to his knowledge of a ancient alien mythology related to the mysterious mecha that the disaster have been averted.

However, it wasn't over that night as one of their guests wasn't happy about the party ending abruptly and refuses to leave. Because of this, they had to challenge him to a basketball game in which whoever scores twenty points first wins.

After a long and grueling battle, Rigby was able to pull off a victory due to a deal with a mysterious being during the break, leading to another trouble as Mordecai and Skips had to go and save him. This would lead to another adventure as the duo risk their lives to rescue the talking raccoon despite the latter being the cause of majority of everything that have gone wrong since 2009.

After it was over, the trio returns to their universe in which Skips warns the two groundskeeper of tampering with the fabric of time and space before heading on home. Minutes later, Benson comes in after returning from an anger management seminar only to find the park mostly destroyed due to the incident with a doomsday mecha the night before and threatens to fire the two if they don't clean up the mess by the end of the day.

Just when Mordecai and Rigby were ready to start, an elderly oversized lollipop named Pops runs around like a hyperactive kid on crack yelling, "Have you two heard? A local farm made a foreign transaction of a cattle from China!" before running off.

"A cow from Asia? I got an idea, let's go to that farm and tip it!" said Rigby.

"I don't know man, you know how farmer Bob is when someone trespasses his property, remember what happened the last time you tried to tip a cow?" said Mordecai, recalling there time when the farmer stormed out of the house and punt Rigby into the nearby farmer's market.

"That farmer was pretending to be asleep and I wasn't ready!" the raccoon yelled.

"Yeah, not only that, you landed into the lemon stand and because of that, you couldn't see for a week!" the blue jay laughed.

"Oh god why did you bring that one up? I can still remember the sting in my eyes!" Rigby yelled in horror.

The two then heads off to the farm where they came upon a cattle that neither had seen the last time they came to visit.

"That cow looks different." said Rigby.

"I don't know, I think that's an ox...so it'll look different." said Mordecai.

"Ox, cow, whatever, it's still the same thing, let's tip it before the farmer finds out!"

But then, the ox got up and immediately pulls out nunchukus in each of the front hoof, demonstrating his martial arts skills in a blazing speed. The two park groundskeepers became intimidated as the cattle made it clear that it won't be pushed around without a fight and made series of acrobatic stances before hitting Rigby with a single strike, send him flying into the lemon stand.

"RIGBY!"

The ox turns his attention toward the blue jay and leaps into the air, landing onto the tree branch right above him.

"Whoa, cool." said Mordecai.

The ox then leaps down and slams the weapon onto Mordecai's head, causing him to black out.

The next day in the hospital, the blue jay woke up and groaned, "Aw man...what happened?"

He then saw Benson, Skips, Pops, Muscle Man, and Hi-Five Ghost in front of him.

"Hey, what are you guys doing here?" he asked.

The gumball machine growls and said, "You two idiots were supposed to be cleaning up the park but instead you decided that trying to tip over an animal at the farm is more important."

"Once you guys recover, I expect you to clean up the park or you're FIRED!"

This woke Rigby up, causing him to jump out of the nearby bed in a jolt.

"Oh, it's you...so, hey guys."

Then the entire building shook.

"What the?"

Everyone looked out the window to see a giant lemon monster tearing up the city.

"Hey, that looked just like that coffee guy we met few years ago!" Rigby shouted.

Skips turns to glare at Rigby and said, "What the hell did you do this time?"

"What? Why me? What did I do?" the raccoon yelled.

"That's because most of the phenomenon that occurred in the past several years have been your fault, what have you done this time?" the yeti yelled.

"Nothing!" was the answer.

"We went up to the farm and tried to tip an ox and got beaten up, Rigby was knocked into a lemon stand!" Mordecai yelled.

"Dude!"

"I'm sorry Rigby but this is the only way Skips can help us!"

"Then that lemon monster is after you!" yelled Skips.

"Why?" Rigby yelled.

"That's because you crushed too many lemons and now this creature have emerged to exact revenge against whoever committed the atrocity to its kin!"

Meanwhile, the giant lemon monster was squeezing out lemon juice out of its nipples, hosing the city and blinding many people who didn't close their eyes in time. It didn't take long before the gang fled from the hospital before the lemon monster turns its attention toward the building, destroying it with a burst of lemon juice from its mouth.

"What are we gonna do?" yelled Rigby.

"I don't know, it won't stop until it kills the one it's looking for." said Skips.

"You don't know? Then how are we gonna stop that thing?" Mordecai yelled.

Then suddenly, Rigby has an idea.

"Wait, I got an idea!" the raccoon yelled.

The blue jay and the yeti realize what Rigby was talking about.

"Oh no, no way man, remember what happened last time you tried that?" said Mordecai.

"C'mon man, I have another calculator with me this time!" the raccoon yelled.

After watching the lemon monster continuing to wreak havoc on the city and has set its sights toward the park, that's when Skips said, "We don't have a choice, it could be the only way to stop that monster!"

Giving it a thought for a minute, the blue jay then narrows his eyes and said, "Guess we really have no choice...Rigby, let's do this!"

"Yeah!" Rigby shouts.

The gang then drives off to rent a helicopter.