Most of the Asians shown are based off of stereotype. The waitresses from "Fortune Cookie" are the most blatant. They have small eyes, and talk in a way that mocks Chinese.
Pops is clearly based on stereotypes of the English, though it is clear that he is insane.
British rock star characters feature regularly, in an example of positive stereotyping.
Negated Moment of Awesome: Deconstructed in 'Meteor Moves'. The Guardian of The Friend Zone shows Mordecai the various moments where he had a great opportunity to kiss Margaret (or at least tell her how he felt about her) but didn't.
Rigby: (weakly) I thought if I ate really fast, maybe I wouldn't notice. I just really wanted that hat.
"Picking Up Margaret"
Rigby: Margaret, these eggs are GOOD!
And in "One Pull Up," Rigby drinks a glass of raw eggs!
Don't forget the Halloween Specials, where the park staff are killed off at the end, but they come back absolutely fine in the next episode.
Skips uses a computer to look up the Play Co Armboy in "Over the Top", but in "Skips vs Technology" he doesn't even know what an icon is.
Near Death Experience: Pops in "Prankless". Muscle Man taped a bed to the ceiling to trick Mordecai, but the tape gave way just as Pops ended up chasing a balloon into the room, resulting in Pops being crushed. He survived by a slim chance.
Nice Job Breaking It, Hero: Rigby is usually the one who causes the crazy bleedly-blah to happen in the show. By this point it should be obvious that Rigby ruins everything he touches, though he does make up for it by fixing most of the mistakes and problems he creates such as giving up the chocolate cake to save Skips' life and using mustard to defeat cannibal hotdogs. Examples include...
sending Skips to the moon, which almost got him and the rest of the cast killed by a giant monster in "The Power."
letting the Destroyer of Worlds loose (despite Skips and Mordecai's warnings) in "Just Set Up The Chairs".
signing the contract that almost made them lose their concert tickets, though it technically wasn't his fault since he couldn't even read it, in "Caffeinated Concert Tickets".
interrupting Skips' spirit dance in "Free Cake".
nearly making Mordecai freeze to death in "Meat Your Maker".
starting a lying competition with Mordecai which unleashes antimatter in "Grilled Cheese Deluxe".
breaking the audit machine nearly getting the park deleted in "Don".
alluding a bodybuilder without his body that his own body was still available in "Rigby's Body".
changing the Book of Park records and getting killed in "Appreciation Day".
drawing on Pops' face with Sharpie and knocking him out in "Dizzy".
getting Benson fired in "Benson Be Gone".
getting lame songs stuck in his head in "This is My Jam".
allowing a doppelganger to steal his image in "Temp Check".
using his solids to ruin Mordecai's date by destroying the house in "Do Me a Solid"
putting in the tape backwards and unleashing the dead in "Grave Sights".
sneaking out to RRW Wrassle Frassle VII in "Really Real Wrestling".
cheating on the bet and getting Mordecai blonde in "Bet to Be Blonde".
egging the wizard's house in "Terror Tales of the Park".
making Mordecai drive into the RESTRICTED section of the park in "Camping Can Be Cool".
switching fortunes with Benson in "Fortune Cookie".
eating a huge omelet despite his egg allergy in "Eggscellent".
changing his name to Trash Boat in "Trash Boat".
breaking Skips' hands in "Fists of Justice".
opening his eyes and unleashing Margaret's Guardian of Secrets in "Diary".
pranking Mordecai and unleashing Death Bear in "Death Bear".
Mordecai kicks off his share of weird events as well, though it's usually due to pettiness instead of outright idiocy. In both "Death Punchies" and "It's Time", it's his pride that goes before the fall. Rigby's, that is.
Benson gets one in "Peeps", when he keeps improving his security system to stop Mordecai and Rigby from slacking off (justified though) and ultimately doesn't read the fine print and invites an Eldritch Abomination to spy on the park's workers for the rest of their natural lives. Ironically, the very thing he tried to stop them from doing is what got rid of it.
Skips in "Over the Top", when he literally kills Rigby, thus forcing him into an arm wrestling match with Death himself to bring Rigby back from the beyond.
Skips gets one again in "Sugar Rush", when Pops gets a sugar rush, he tells Mordecai and Rigby to give Pops more sugar so he can get a sugar crash but it causes Pops to move so fast that the world slows down to him.
No OSHA Compliance: Highway 13, the most dangerous highway in the country. Whoever designed it made sure to make it a natural obstacle course starting with a decayed bridge built over rapidly eroding soil, potholes, random nails sticking up out of the ground, platformed sections of road crossing over a Bottomless Pit, an obstacle course of stalagmites, and giant craters containing a nuclear green glowing vortex at the bottom.
Noodle Implements: In "A Bunch of Full Grown Geese", when Mordecai and Rigby get geese repellant on them and smell like rotten eggs, one of Skips' first instruction to get rid of the smell was for them to drive to the ocean.
The cart, the shoes, the party, the other party...
Dr. Asinoskovich doesn't like to talk about that conference.
"Appreciation Day" has this as they're reading the Park Records:
Mordecai: Destruction of park property?!
Rigby: Oh, yeah, that one time!
The solid worth ten solids that Rigby made Mordecai do. All we know is that all who witnessed it were shocked and repulsed, and it involved Mordecai squatting down and making car sounds. Fan speculation says that it was either him laying an egg or LITERALLY "doing a solid" (taking a dump)
In "Quips", Skips tells Mordecai and Rigby they owe him for the time he rescued them from a pack of glowing red-eyes wolves, when the cart and themselves were stuck in quicksand, and the time he carried them out from a creature while being chased by a group of winged heads that look like Pops.
Nutritional Nightmare: In season 3, "The Best Burger in the World", a food truck makes a burger once every century called the "Ulti-Meatum" where they stuff a cheeseburger inside a cheeseburger and has two deep-fried cheeseburgers as buns. They can even make it Idaho-style by stuffing a bag of chips in the burger.
Of Corpse He's Alive: The episode "Weekend at Benson's" has Mordecai and Rigby having to "escort" an unconcious Benson to a party after accidentally knocking him out cold at work.
Official Couple: Mordecai and Margaret as of "Meteor Moves". Officially dead as of "Steak Me Amadeus".
Now it's Mordecai and CJ as of "I Like You Hi" and it was solidified in "Real Date".
Off Model: The pilot episode showed up again later with some added parts to lengthen it to fit with a standard episode. Between the new scenes and the old scenes, characters change appearances pretty noticeably, due to the pilot having a looser animation style.
The initial broadcast of "Power Tower" aired with a serious color saturation problem, as well as the animation being generally unfinished (due to an unfinished version of the episode being mistakenly shipped out). See for◊ yourself.◊
Older than They Look: As of "The Night Owl", Mordecai, Rigby, Muscle Man, and High-Five Ghost have aged another 2200 years, having been frozen with liquid nitrogen, unfrozen in the year 4224, and then time-traveled back into the past. Potentially subverted if the show followed the other group from the end on.
Skips, who could be thousands of years old.
Techmo. Considering that Skips fixed his arm back in 1783, that would make him well over 200 years old.
Thomas, the son of Death, has the appearance of an toddler, but is really over 300 years old and is only playing immaturity so that he can be taken care of.
Subverted; although every video game shown so far has had retro graphics, this seems to be a stylistic choice, befitting the show's Retraux style and suggesting that maybe everyone in this world is just a retro gamer.
Lampshaded in Sarcasm Mode when Mordecai and Rigby comment on the graphics and how the title screen looks just like the box.
In "Over the Top", they're even seen playing what appears to be an 8-bit version of Guitar Hero.
This is all especially subverted by the fact that Mordecai and Rigby very clearly have a Sega Master System Mark 1, which is most certainly an obscure version of a games console to have.
Paper-Thin Disguise: Apparently, in "New Year's Kiss", Mordecai and C.J.'s masquerade masks were so convincing that neither of them didn't recognize each other and were surprised to see each other when they removed their masks despite one being a blue jay and the other being a cloud humanoid.
Twice in "Rigby's Body", once by the bodybuilder that jumped into Rigby's body and again by Skips. His nipples light up.
Mordecai gets one too when he daydreams in "Meat Your Maker".
Muscle Man does this in "Bald Spot". For a long time, I might add.
Rigby does this after he gets buffed up in "One Pull Up".
Percussive Maintenance: Skips' main method of fixing things is to hit it with a hammer. To be more specific, he carries a hammer that he's able to use as a universal tool to fix almost anything, regardless of how big or small it is, including computers.
Petting Zoo People: Mordecai is the most obvious example, but Margaret and several background characters also qualify.
Pilot: "First Day" is the Pilot with some added bits: a montage at the beginning, a scene before they go down for breakfast, and a scene with Muscle Man and High-Five Ghost, to make it a Whole Episode Flashback.
Pink Girl, Blue Boy: Mordecai is bright blue. Margaret, his love interest, is bright red, which isn't exactly pink per se, but close enough.
The Plan: Of all people, Muscle Man surprisingly shows up with more than one of these
Evil Plan: Muscle Man's costume party was simply a ploy to get back at Mordecai and Rigby for spilling soda on his face.
Plot Tailored to the Party: The Christmas special- in order to reach the lava, the group needs Benson's skills in non-video game arcade games (as seen in 'Stick Hockey'), Pops' wrestling abilities (as seen in 'Really Real Wrestling') and Muscle Man's Dance Dance Revolution-esque skills (as seen in 'Fuzzy Dice').
Pokémon Speak: The giant coffee bean can only say his name. And his name is Coffee. Possibly lampshaded by the fact that his translator is Japanese.
Power Fist: The "Fists of Justice", in the episode of the same name.
The Power of Friendship: That seems to be the theme in "Eggscellent". Even when Rigby was in a coma, possibly never to wake up and even may die, Mordecai still keep his promise to get that hat for him. Then the other Groundkeepers came around for Mordecai when he couldn't do it alone and helped him practiced to win the hat. When Mordecai won the hat, he put it on his friend's head, which woke him up! It wasn't just because of the hat, it was also because of Mordecai's loyal Friendship for Rigby!
The Power of Rock: The battle between Mordecai's band and the Summertime Song is manifested as two ethereal rockers using their guitars as swords.
Pops' The Realm of Darthon character, a cybernetic cowboy, utilizes a keytar as a weapon which shoots Frickin' Laser Beams when played.
Punched Across the Room: Rigby does this to various bystanders in "Death Punchies" after he learns the appropriate Death Kwon Do move, the 'Death Punch'.
Putting the Band Back Together: In "Exit 9B", after escaping GBF Jr. by time traveling two months in the future, Mordecai and Rigby must bring the brainwashed park workers back to their previous selves and unite them to save the park.
High-Five Ghost doesn't talk very much, only having two lines in his first 5 or so appearances. However, he spoke more in "Muscle Woman" than in all of his previous appearances combined.
Justified in that he was jinxed.
The Quincy Punk: Appear from time to time, but the four known as Trash, Scabatha, Manslaughter, and Bloodshed in "Cruisin'" are particularly notable.
Raiders of the Lost Parody: One episode ends with Mordecai forced to choose the correct hat out of a collection of other hats in an obvious homage to Indiana Jones and the Last Crusade, down to an aged knight watching over the proceedings and the fact that he'll be skeletonized if he chooses poorly.
In "Peeps", Benson asks for the most powerful security system Peeps will offer and is told to sign a binding contract. He's so angry he doesn't read it first and ends up summoning Peeps himself (a flying eye monster). Peeps later reveals the contract states he can watch them till the day they die.
In "But I Have a Receipt", Mordecai and Rigby try to return The Realm of Darthon but they didn't read the fine print. They already opened the game.
Reality Warper: The Power grants people... the power to do anything they want. Also, the Master Prank Caller, who should not be riled.
Reality-Writing Book: Forging the park records has this effect. Mordecai and Rigby do it to trick Benson into giving them a raise, but Rigby overdoes it, resulting in the park being attacked by a snow monster.
Reason You Suck Speech: After trying so hard not to get mad and yell at Mordecai and Rigby because Pops grows sick of it, all of the rage builds up inside of Benson, and he lets out a ear-rapingly brutal RYS at the duo, deafening them.
In "Caffeinated Concert Tickets", Mordecai and Rigby give a Karma Houdini diss against the coffee bean and his translator, ending it with a "Your coffee... sucks," while pointing at the guy's crotch.
Recurring Character: Other than Margaret, Elieen and Mr. Maellard, there's also Pa (the man who was kicked by the ostrich in "Grilled Cheese Deluxe") and one of TV Store Warehouse spokesman (the bald one)
Relationship Upgrade: "Butt Dial" marks the first time Margaret actually acknowledges Mordecai's crush on her, as a result of hearing an accidentally recorded voicemail where he sings about it. In Picking Up Margaret the two finally kiss.
Retro Universe: Everything has a very '80s feel—any video games that show up are extremely retro and/or arcade-based (see Pac-Man Fever above), VHS and casette tapes abound, and if a licensed song shows up it's guaranteed to be a hit from the '60, '70, or '80s—but it's set in the present. "Prank Callers" places it after 2004 somewhere.
In "The Best VHS In The World", the video store they frequent is stated to be the only one still renting cassettes, with all the other stores having converted to DVDs.
Ridiculously Difficult Route: In "Busted Cart", to make up for lost time and to get the cart fixed before the warranty expires, Mordecai and Rigby take Highway 13 to get to the dealership faster. It's considered the most dangerous highway in the country due to the road crumbling, spikes on the road, giant boulders rolling down the valley, and a crater with a green portal in the center.
Ripple-Effect-Proof Memory: In "A Skips in Time", Muscle Man is able to remember a friend with a time machine who went back in time and accidentally prevented his parents from ever meeting, wiping himself from existence.
Roommate Com: The show focuses on two guys performing wacky hijinks while living in a rented house with their coworkers. Even with all of the supernatural happenings there, it ultimately always goes back to the premise of roommates.
Satellite Love Interest: In the entire first season not much is known about Margaret, except she's nice and has a good set of lady pecs. Justified in that Mordecai himself can't seem to get past his shyness and learn more about her besides how attracted he is to her. (Note that he's always completely surprised about her boyfriends and entertainment preferences.)
Shaggy Dog Story: Several episodes. In "A Bunch of Baby Ducks," the entire episode revolves around Mordecai and Rigby trying to get rid of the titular baby ducks so they can finish cleaning out the fountain. As they reported at the end of the episode, the good news was they got rid of the baby ducks, but the bad news was the fountain was destroyed.
"Slam Dunk" also has this plot element: Mordecai and Rigby battle Muscle Man and High Five Ghost for coveted time on the house computer, so that Mordecai can make a website for Margaret. After a climactic battle including a from-orbit slam dunk, Mordecai and Rigby win, Mordecai approaches Margaret, and find out she already made the website, since she asked two months ago.
Basketball Coach: Time goes faster in space.
"Every Meat Burrito:" the gang want to try a famous "every meat burrito" from a new restaurant, but the drive-thru clerk won't let them because they don't have a real car. After borrowing an old car from a police impound lot, and dealing with the crazy guy from the 1970's who's been living in the shag carpeting, they finally get to try it...
Screw the Rules, I Have Money!: In "Country Club", the country clubmembers are a bunch of Rich Jerks who believe that they can mess with anyone, steal anyone's prized possession, and turn said possession into a toilet all for their amusement just because they are rich.
In "Cool Bikes", Mordecai and Rigby become so cool that it threatens to create a coolness singularity which will collapse Earth into a coolness black hole and destroy the universe.
In "Fortune Cookie" Benson has such bad luck that he loses the park to a sorcerer who then immediately grows over fifty feet tall and begins to literally suck up the entire park into his fanny pack. Yeah...
Series Continuity Error: "Eggscellent" reveals that Rigby is deathly allergic to eggs. He eats eggs after this episode, however (such as in "Picking Up Margaret"), and some episodes before it have him wanting to eat food that contains eggs, like cake.
Zigzagged with "Power Tower", the episode dedicated to Muscle Man's past as a bodybuilder. It starts off as being about ping pong, then switches to being about bodybuilding, which is Serious Business in real life. Then Riley and Mordecai point out that all the effort MM's putting in isn't worth a ping-pong game, and he says its not really about ping pong any more. Then he finds a technique so advanced that the last guy to try and use it ended up killing himself in the process by "shredding every muscle in his body", bringing it right up to the show's usual levels of this trope.
Ship Sinking: After numerous instances of Ship Tease, the Mordecai/Margaret ship was finally sunk in Steak Me Amadeus. For now, at least.
The Pretty One — Mordecai (He's got quite a few fangirls)
The Smart One — Benson
The Wild One(s) — Muscle Man and High Five Ghost.
Oddly enough, Muscle Man is not The Muscle.
Skewed Priorities: Dude, you kill the Destroyer of Worlds! I'm gonna go get the chairs!
Slice of Life: The show is basically about the lives of two best friends who are groundskeepers. Simultaneously a Work Com, as they live where they work. Every episode so far has had something to do with their job, although it's usually not what Mordecai and Rigby are interested in.
Smelly Skunk: A Jerkass one tries to turn Rigby into a skunk. Well sort of, he's a Wereskunk whose spray transfers his curse in addition to smelling terrible. He's cured along with Rigby in the end, but it's implied he died in the process.
Stalker with a Crush: Eileen to Rigby. First noted in "Do Me A Solid", when Mordecai notices that Eileen is staring at Rigby from the other side of the Coffee Shop.
Subverted in "Diary", Margaret forgot to tell Mordecai and Rigby that she asked Eileen to water her plants since she had the guest room for the weekend. The night before Margaret revealed this, Rigby confessed that his biggest secret was that he thinks Eileen is hot without her glasses on. Guess who comes to serve their coffee without her glasses?
This was subverted in the fact that Eileen heard Rigby say this while she was (unknowingly to Rigby) in the guest room
"Trucker Hall of Fame" begins with Muscle Dad's death.
Status Quo Is God: Mordecai and Margaret's relationship seems perpetually static. No matter how many moments they share together, no matter how much time they spend together, they still aren't dating and still act sheepish around each other. Even Mordecai singing a song about how hot she is, how much fun he has around her, and directly saying that he'd like to be more than friends doesn't seem to change anything. The same situation is with Mordecai and Rigby's job - Benson always tells them it is their last chance to do something right or they'll be fired. How they are still employed is a mystery.
Stealth Pun: In "Really Real Wrestling," one of the wrestlers Mordecai, Rigby, and Pops fight is a wrestler who's dressed in a fireman's hat and can breathe fire. He's called the Fire Fighter.
More than that, Pops beats him using a wrestling move called a Fireman's Carry.
In the first Halloween ep, the final story has Muscle Man flayed alive without any skin left. He really was a Muscle Man.
In "Exit 9B", GBF Jr. builds an exit ramp to a portal that releases all of the deceased villains from the center of the earth. In other words, it's a Highway to Hell.
Stuff Blowing Up: In "A Bunch of Baby Ducks", a man explodes after being karate-chopped. With a mushroom cloud and everything. The show is usually much less egregious about this.
Benson: Muscle Man, have you seen Pops at all today?
Muscle Man: Yeah, and you know who else has seen Pops today?
Benson: (dryly) Who, your mom?
Muscle Man: I wasn't gonna say that! Why does everyone always think I'm gonna say "my mom"?
Suck E. Cheese's: One is featured in "Fuzzy Dice". Bonus points for the crappy animatronic animal band being a group of criminals who were waiting for the right moment to snatch the Fuzzy Dice for themselves and the uncut diamonds found within.
Suck Sessor: Jeremy and Chad of "Replaced." They are actually able to complete Mordecai and Rigby's jobs despite constant interruptions and distractions, however at the end of the day they decide that the job is just not worth the hassle.
Superstition Episode: The episode "Fortune Cookie" shows Benson getting a streak of good luck, while Rigby gets the opposite. When the group visits a Chinese restaurant and Benson gets a fortune of good luck while Rigby gets the opposite, Rigby becomes jealous and switches the fortunes when Benson's not looking. Benson reads his new fortune, which predicts bad luck, and mindlessly discards it. The rest of the episode shows Benson on a streak of bad luck, with Rigby getting the opposite.
Suspiciously Specific Denial: In "Peeps", when Mordecai list responsible things Benson can't trust them to do, Rigby "helps" by mentioning that they also can't be trusted to not fart in Benson's coffee when he's not looking.
Too many TVs! Take your pick! We're practically giving them away! No, wait! We're literally giving them away! LITERALLY! We're practically literally giving TVs away! Literally!
Sword Cane: The Creepy Duck Man owns one that he uses to threaten Mordecai and Rigby after they crash his truck.
Take That: Dudetime Cologne from "The Unicorns Have Got to Go" is a pretty clear parody of the advertising for AXE body spray. It's probably not a coincidence that it attracts jerkass unicorns instead of hot ladies.
In "Video Game Wizard", when Rigby tries out the new power glove they won at a video game tournament, he notices how it doesn't work... just like the actual Power Glove. "Dude, this glove sucks!"
In "That's My Television", the network that holds RG-B2 against his will is likely an exaggeration of the strategies of other networks.
Rigby: How am I doing? Huh, Mordecai? Am I doing all right? "Yeah, Rigby, you're doing good!"
Telephone Teleport: In the episode "Fool Me Twice," the phone number that Mordecai and Rigby have to call for their chance to participate in a Japanese game show has to be called from a landline. As it turns out, it's because the "lucky" contestants get transmitted through the phone line straight to the studio.
Temporal Paradox: This happens when Mordecai and Rigby refuse to lip sync a song that Future!Mordecai and Future!Rigby claim is not only the reason for their success, but entire existence. The two future beings then disappear after Mordecai breaks up the band.
Skips does this during a video game tournament when Mordecai tries to switch him out for Rigby on the excuse that Skips' hand was hurt.
Referee:"His hand doesn't look injured to me."
*Skips punches the metal wall, then removes his mangled hand from the hole.*
Skips:"Wanna check again?"
Time Dilation: In "Slam Dunk" Mordecai and Rigby play basketball against Muscle Man and the God Of Basketball and their game ends taking them into space,once they come back down to Earth they find out that they've been gone for 2 months
Time Travel: In "It's Time", after Mordecai kills Rigby.
Again in "Bad Kiss", to prevent Mordecai and Margaret's first kiss using a time machine that Rigby bought for fifteen dollars.
"Trash Boat" sees Rigby targeted by a rock star from the future dead set on killing him for stealing his fame prematurely.
To Hell and Back: Muscle Man's brother John rides his truck out of Hell to scold Mordecai and Rigby for insulting his mom.
Susan rises straight from Hell after Benson thought he killed her.
Arguably Benson in his Day in the Limelight episode "Benson Be Gone", especially when he takes a limo and tries to run down the One-Winged Angel version of Susan, dying in the process.. Leon takes his place at the last minute, but still!
Benson takes another level in badass in "Stick Hockey", where the titular game is apparently an underground bloodsport complete with rampant death, burning pits, and lots of spikes.
A promo for Season 4 revealed that in "Terror Tales of the Park II," Jan is actually a giant man-eating spider.
True Companions: There are moments when the group seems to be close to or evolving into this. While they don't always get along, they are shown to really care for one another at certain moments, such as Benson facing off against Susan to save them all and nearly making a Heroic Sacrifice to do so (Utopia took his place, but its clear) and the climax of "This Is My Jam" when Skips and the others come to help defeat the living Ear Worm without even being asked.
T-Word Euphemism: "How in the H are we gonna get rid of this S?" in the first episode. H is also used in later episodes.
Rigby: What a windbag!, I thought he’d never shut up. I can’t believe you guys thought he was me. You must feel like idiots, right?
In "Fortune Cookie", Rigby's streak of successes leads him to become an arrogant jerkass. In actual fact it's only because he had a streak of good luck, that he only got by being switching his "bad luck" fortune cookie message with Benson's "good luck" one (which caused Benson to have a streak of bad luck).
Unicorn: "The Unicorns Have Got to Go." They're punky/gothy Ambiguously Gay party animals who substitute periods with "bro" and are attracted by the scent of DudeTime cologne. They also never say no to drag racing.
The Unreveal: The setting of the show. In "Prank Callers", after traveling back in time to 1982, the gang gets back to their own time by looking at which door holds their time period. Theirs is simply named "Present Day".
Though most of it isn't heard, Thomas' story at the start of the third Halloween special is obviously based on the urban legend about the Killer Inside The House. Though he messes up the Wham Line "The call is coming from inside the house" by saying "The call is coming from outside the house" first.
Vague Age: Averted in the first episode, where it's revealed Mordecai and Rigby are both 23 years old. The other characters, however, have no set age. The closest we know are from the storyboard artist's Formspring pages. Pops is over 100, Skips is hundreds of years old, and Benson is anywhere from 25-35.
Villain Team-Up: In "Skips Strikes", the bowling team Mordecai, Rigby, Skips, and Benson have to beat is made up of Death, the leader of the Guardians of Youth, Gary, and the wizard Rigby stole The Power from.
"Exit 9B" has Garret Bobby Ferguson Jr. open a portal to the underworld, resurrecting all the previous villains. Strangely, the unicorns aren't among them.
Villainous Breakdown: In "Go Viral", The Warden of the Internet goes berserk after seeing that Mordecai and Rigby had freed all her prisoners.
The Virus: The fate of anyone attacked by the monster in "Jinx".
Techmo in "Skips vs. Technology".
The white creatures in Guy's Night will turn you into one of them if they bite you.
Weirdness Magnet: Mordecai and Rigby. No matter how mundane their assigned task, no matter how minor their everyday, humdrum problem...they somehow find a way to transform it into a beautifully strange epic adventure.
Wham Episode: "Steak Me Amadeus" Mordecai finally works up the nerve to ask Margaret to be his girlfriend. Even in the midst of sting operation and a shootout with the automatrons from "Fuzzy Dice". However she reveals her dream college finally accepted her and she won't have time to commit to him thus she gently let's him down. Needless to say Mordicai is left depressed in the aftermath.
"New Year's Kiss" Rigby tries to stop Mordecai from kissing an unknown girl on the advice of his future self. At first he thinks it's the girl they met at the coffee house who later reveals she was just stringing Mordecai along just to make her former boyfriend jealous. The whole thing turns out to be point as Mordecai figures its out on his own...but then he runs into a girl who kisses him on a whim . When unmasked, it's revealed it's CJ, the girl Mordecai was courting to try to forget about Margaret in Yes Dude Yes leading to a very awkward moment.
Wham Line: In "House Rules", When Future Mordecai tells his present self "...You know what else you're gonna miss? That guy (Rigby). Enjoy him, while you got him. You know what I'm saying?"
Two in "Eggscellent"; When Rigby falls into an allergy induced coma, Benson says that this should teach the others to not slack off their jobs and do something stupid. Mordecai decks him for this and tells him that the rest of the workers are just friends with him because he's their boss.
At the end of "Portable Toilet", Rigby remarks that "CJ's really cool", and Mordecai replies, "Yeah. She is." Even though they're Just Friends, he still has feelings for her!
What Did I Do Last Night?: "Karaoke Video" starts out like this. Mordacai and Rigby don't remember saying any of the mean things to their co-workers while they sang "We're Not Gonna Take It" by Twisted Sister. They only find out when they replay the tape of their performance the next day.
Mordecai didn't remember ordering fake band t-shirts in "Mordecai & The Rigbys," either.
Who can forget their wild orgy-like party in "Replaced" that Benson yelled at them for?
What Happened to the Mouse?: In "Guy's Night", Thomas is sent out to get chips and just disappears for the rest of the episode. How long does getting chips even take?
Father Time gives one to Mordecai after Mordecai kills Rigby by thowing him into the time stream.
Mordecai himself gives one to Skips after Skips kills Rigby in a bought of rage.
Mordecai, Rigby and Skips all give Benson this treatment after he gets rid of Mordecai and Rigby's stick hockey table, even after he gave them his word he wouldn't get rid of it if they did their work and didn't wait to see if they would.
Benson gets another one in "Eggcelent" after he claims that Rigby being put into a life threatening coma is his own fault. Mordecai actually punches him and tells him that the only reason anybody puts up with him is because he signs their paychecks.
Mordecai gets this from Skips in "Video Game Wizard" when he jeopardizes his friendship with Rigby to win the Maximum Glove.
Where The Hell Is Springfield??: The location of the city where the series takes place doesn't have a clearly defined location—in fact, the city appears to be named "City", not an actual name. All we know about it is that there's a large desert (multiple episodes) and a national park ("Camping Can Be Cool") nearby, and that it's 94 miles from a major convention center ("Video Game Wizards"). As for location, the closest we have is in "Prankless" where the rival park's (East Pines) command post shoots into space as part of Muscle Man's prank, and an image of the city is shown over the Midwest, closer to the south (possibly in the Sun Belt region). Radio call signs also start with "K", putting the location west of the Mississippi River. In "Firework Run", the guys also travel south to get fireworks from a Latino person. Given the above, it's likely that the town is located in Texas, New Mexico, or even Arizona to be close to the Mexican border. In "Skips vs. Technology", during 1783, the park was a battleground during the American Revolutionary War so the location has to be somewhere that was part of the war at the time. In "A Skips in Time", the park and city are hit by a tornado, further reinforcing they're in the Midwest and likely Texas specifically (although tornadoes can happen almost anywhere in the continental United States, they're just much more common in Tornado Alley).
Skips gets similar treatment by the final zombie of the Zombacalypse episode.
This also happens to Skips and Muscle Man when Rigby learns the Death Punch.
X Called; They Want Their Y Back: A Running Gag in the prank calling episode: "The [decade] called. They want their [object] back." This being the show that it is, saying that literally sends the object in question back to the decade.
Xanatos Gambit: Muscle Man's seemingly innocent "My Mom!" catchphrase is actually a setup to prank anyone who tries to correct him and tell him the joke is normally ended with "Your Mom!". The prank involves calling his brother, who drives his truck out of the pits of hell, and making the prank victim apologize and kiss a picture of their mom... which is really just a picture of Muscle Man's ass. On the other hand, if they don't take the bait then he gets to annoy them by saying it over and over again, which might be just as bad.
You Need a Breath Mint: In "Bad Kiss", after Mordecai and Margaret kiss, Margaret says she didn't enjoy it because his breath was bad. When he tells Rigby, he scolds him for not using a mint before doing the deed.