In "Free Cake", Rigby says something along the lines of "Did you go to medical school in the last five minutes?" exactly five minutes into the episode.
During the commercial for Fist Pump in "Caffeinated Concert Tickets", the announcer mentions that Fist Pump's demographic is people within the age range of eleven to fifteen. However, the end of the episode shows the concert to be completely full of adults, with absolutely no adolescents in sight. Regular Show itself has a similar scenario - it's on Cartoon Network, which is primarily a kids' network. However, the more mature level of humor and content (like Fist Pump's declaration of having been just been released from jail and rehab) causes it to primarily be viewed by an older audience. It's all a Lampshade Hanging on Regular Show's own demographics!
Also, eleven to fifteen year olds is the show's own demographic, which adds to the brilliance.
You can also think of it this way - during the entire episode, the characters comment on how this is a band that "was cool back when they were younger". The entire crowd at the concert are probably all the old fans, since they're outdated and aren't attracting any new ones.
Doubles as Fridge Logic when you remember how Cartoon Network had came under fire before in the last decade for their hypocritical practices of using live-action and a fair share of unpopular new shows killing off the classics; in summary, it was their existence being, quoting Peter Griffin, "a little hipper to bring back those boys you scared away."
May not be Fridge Brilliance, or intentional, but most people are always pitting Regular Show and Adventure Time against each other. Well, if you know AT, you know Finn, Ice King, and possibly Susan Strong are pretty much the only humans. But in Regular Show, all the main characters are either non-human or some weird human. However, almost all the other character extras are humans with no notable differences. It could be a coincidence, or it could be the animators intending Regular Show and Adventure Time to face with each other.
For Pops' horror story in the Halloween episode, it was pretty flimsy and flat for a "scary story". Then I realized that Pops probably gets scared by horror movies pretty easily and only catches them in glimpses. And when the evil doll said "Mark on your face", it could have been easily "Carve your face" so Pops wouldn't be scared of his own story.
Proven in the second Halloween special, with Pops being scared at even the smallest scary story detail.
In "Do Me a Solid", Mordecai and Rigby get into a sort of war based on favors. Eventually, under the threat of the world ending, Mordecai is forced to do one last embarrassing task of Rigby's in front of everyone. This task involves squatting down and making sounds similar to an airplane backing out of a runway. It's pretty obvious what that signifies. The brilliance? MORDECAI WAS DOING RIGBY A SOLID.
Using The Beach Boys' "I Get Around" in "Skips Vs. Technology". Considering that most of the music the show licenses is from the 80's, The Beach Boys (who were most active in the 60's) could be considered outdated for this show, just as Skips considered himself outdated in the episode.
In "Video Game Wizard", Skips is shown to be really good at video games despite him rarely playing it. Why is that despite him having trouble using a computer? Because in "Fist of Justice", the controls of to the "Fist of Justice" are similar to a game controller and he has to use them every 157 years to fight The Guardians of Eternal Youth's evil brother, Klordbane.
"My Mom" shows Muscle Man, who Mordecai considers just a Fat Idiot, supervising Mordecai and Rigby. He does an excellent job of that: shows them how they can slack at the job as long as they have won Benson's trust and really accomplish the missions he assigns. Also that Benson, as the boss, deserves to be informed about what his employees are they doing every time. Muscle Man even broke traffic laws because he knows the cop is his friend. He asked the guy at the greenhouse to carry the tree (because it's his job and he knows how to do it right) and even treats Mordecai for the videogames. The thing that makes Muscle Man borders Magnificent Bastard is that his "joke" is a Batman Gambit: If Mordecai would not have used his Condescending Compassion with the "My Mom" jokes, he and Rigby really would have enjoyed Muscle Man's "supervision". So, if like Muscle Man, you can be a Slacker immature guy but if you could not get respect from your coworkers, at least you could get revenge.
Muscle Man's plan to get revenge on Rigby and Mordecai in "My Mom" and See you there both involve a Batman Gambit: If Rigby and Mordecai would not treated Muscle Man with Pity Perversion or accepted Muscle Man's decision to not invite them to HFG' party, they would not have been humiliated so badly and Muscle Man would have get a great time anyway. He spent considerable resources, but he would have won in any scenario. A true Magnificent Bastard?
For part of Dead at Eight, Rigby carries Muscle Man around his neck, in the form of Death's soul-containing amulet. In Muscle Mentor, Muscle Man returns the favor by carrying Rigby in the "Mentoring Harness."
In "Cruisin'," Mordecai and Rigby sport cheesy smiles to feign confidence. When Rigby points out that "no human ever makes this face," two women immediately get in their car. Of course, the faces worked because Rigby and Mordecai are not human.
In Fancy Restaurant, Starla's parents always seem to follow Muscle Man's cue. This would seem table manners at first, since Muscle Man is the host, but it also makes a lot more sense after the reveal that they are not fancy either and just imitating Muscle Man, whom they believe is fancy.
In The Best VHS in the World, we find out Rigby has a bra that he likes to refer to as his butt-cheek pants. This may seem like his usual immature humor, but when you think about it, he may be wearing them due to him being the one-cheek wonder. This is also quite similar to the way women will wear a bra made to make it seem like they have larger breasts.
In 'Exit 9B', Death joins in on the Park's side to combat the army of resurrected villains. All the villains just escaped from Hell, Death was probably doing his job and helping return them to the afterlife where they belonged.
In "Dead at Eight", Death and his wife were pretty mad at Mordecai and Rigby for wrecking their home while they were babysitting their son, Thomas, but they got over it when they see that they got him to go to sleep, despite a glass chandelier being on top of him. So why aren't they that mad at Mordecai and Rigby despite the situation they were in? Because this probably wasn't the first time that this happened when someone babysits Thomas. Death was impressed that Mordecai and Rigby didn't die considering that the previous babysitters all died, thanks to Thomas, and tells them they did a better job than them. So at this point, Death and his wife would be happy to have a babysitter to get the job done.
Death's wife also asks Mordecai and Rigby if they have experiences taking care of "paranormal children", so one should expect these kind of children to cause more trouble than regular ones as Thomas demonstrates.
Rigby having only one butt cheek and being called "The One Cheeked Wonder" is funny enough, but the joke doubles when you realize that he does his work as "Half-Assed" as possible.
In "Carter and Briggs" Rigby says his favorite thing about an action-y, inane, cop show is the realism. Considering the bizarre universe Regular Show takes place in, two cops shouting things about donuts and getting angrish while shooting at helicopters is probably considered realistic.
Also, Carter and Briggs love doing donuts. Think about it. They're cops. And they love donuts.
Same with Muscle Man, he likes doing donuts too, and he likes to eat fatty foods.
Eileen is the only recurring character to wear glasses. She's also officially a mole, "which are known for having terrible eyesight."
In "Mordecai and the Rigbys," Mordecai is singing to impress Margaret- "which is what male birds do to attract females."
In "Cold Cubed", Thomas didn't get brain freeze as quickly as Mordicai, Rigby, and Pops. Thomas is a goat, so he isn't susceptible to it.
Thomas is also a deep undercover Russian agent, meaning he's used to cold.
Many were surprised to learn that Margret's father is a human. This actually makes a bit more sense when you watch older episodes, in which, quite a few of Margret's boyfriends were also humans. It doesn't seem weird to her, dating a human.
In "First Day", there's an added scene where Rigby comments that Pops should just throw the chair away. At first this doesn't make a lot of sense, as we soon see he really wants it. Then one remembers that Rigby is a raccoon, and we've seen him pull things out of the trash before back in "Free Cake". He was likely planning to grab it later and get the chair without a fight.
In "More Smarter", Mordecai and Rigby get so intelligent, they start to see their co-workers as more primitive, far less intelligent beings. Muscle Man is reduced to a manatee, which at first seems like a gag on how sloppy his table manners on. But there's a little bit of Fridge Brilliance... Muscle MANatee!
"Steak Me Amadeus" was pretty depressing, what with Mordecai forced to break up with Margaret after she's been accepted into her dream school, strangely enough, he doesn't seem to act all desperate and allows her to go without fuss, why is this? Because the leader of the Capicola Gang, who had formed a pretty ridiculous scheme to get his revenge on the park, derided Margaret's decision seconds before being killed for good this time around. Mordecai must've realized that if Margaret stayed, she could've ended up like the Capicola Gang leader!
Also in the same episode, it makes sense that the Capicola Gang leader sold Pops the fake coupons because Pops is easily gullible and he has never met the Capicola Gang in person so it decreases the chances for the park workers to find out about them.
In Terror Tales Of The Park III, Thomas has to wear his pizza costume until thanksgiving because he told the worst Halloween story. He continues to wear it until The Thanksgiving Special several shows later, when he takes it off. Being that the episodes are usually standalone in some way, this is surprisingly brilliant continuity.
In "The Postcard", when High-Five Ghost and Celia reunite again, why does Celia look exactly the same from four years ago regardless if it's Limited Wardrobe? She wants to make sure that High-Five Ghost will recognize her after all these years so she kept her appearance the same.
After watching Skip Story one realizes why Skip became so obsessed after losing to Rigby (The absolute weakest person in the park), the last time he was weaker Mona died.
In "Benson's Car," the way Jack talks sounds like a stoner. He even has an earring of a green leaf. Seeing that he's from the future, this might mean that marijuana is legalized in the future!
In "Tent Trouble", Mordecai and Rigby have to replace CJ's $200 tent that they accidentally destroyed. While it seems a lot, they should have at least saved up enough money to buy it so why is it difficult for them to afford it? Rigby seems to be the type who would waste money on ridiculous stuff but what about Mordecai? Later in the episode, we see Mordecai with a new smartphone and considering how some of them are expensive, it's no wonder both of them can't afford the tent.
Also in some episodes, Benson uses Mordecai and Rigby's paycheck to pay for the damages Mordecai and Rigby caused to the park and his car as punishment, like in "Benson's Car" and "Paint Job", so that may also be a reason for their financial problem.
Upon watching Thomas Fights Back, a lot of things make so much sense in hindsight. Thomas was about to get laid off from his intern job at the park, so he devises a plan to get the statue of the park's founder, which was stolen by Gene, back to where it rightfully belongs. He shows surprising competence in this episode, including but not limited to, infiltration, espionage, and even taking down Muscle Man in a quick submission move. Now that The Real Thomas has come out and revealed Thomas is actually a Russian spy, this episode makes a whole lot more sense. Even the fake name he uses to infiltrate Gene's park makes more sense! Nicholas? Nikolai? Even the final words he says in the episode "Mission accomplished" have some new meaning! He was most likely contacting Natalia or a KGB agent that he was allowed to stay at the park so he can continue his mission to prepare the hijacking of the park! Possible retroactive Foreshadowing of Thomas' true nature?
In "Wall Buddy", Thomas was really excited to watch "Carter and Briggs Bust Russia". After "The Real Thomas", it makes so much sense.
In "The Real Thomas", why was Thomas not informed about Russia's true intention with the park? They were worried that he might have conflicting loyalty after spending two years undercover and he would probably not go through with the plan.
In "Muscle Woman" it is shown that Muscle Man and Hi-Five Ghost are responsible for a lot of the maintenance at the park. At the time it seemed like humor because of how much Mordecai and Rigby had to do but upon seeing "Power Tower" you realize that it would make sense for Muscle Man to handle all of that. He was a former body builder so he is used to intense physical activity. As for Hi-Five Ghost he is, well a ghost so odds are he wouldn't have the same physical limitations as a living being.
Ever since the "Eggscellent Challenge" Rigby has been shown to eat eggs and egg based products without any ill effects; Rigby is cured of his coma by the trucker's hat, it probably just cured him of his egg allergy!
Why did Mordecai and Rigby (along with a few others) decided it was time to move on from the park after Pops' death? For Mordecai and Rigby, Pops was there from the beginning, even personally hiring them. He also played a part in how they lasted in the park for so long. After awhile, they began to wonder if being groundskeepers is all they'll ever be in life, but the trip to space and helping Pops' with his final and greatest job/destiny to save the universe and being there for his end, they had a "Life's too short" revelation and decided that for Pop's and themselves, it was time to step out of the comfort zone of the part and chase after what they want in life. Make sense?
I always thought it was a funny visual that the park house is filled with silly paintings/portraits of Pops. I assumed it was just a whimsical background design choice on part of the artists on the show. Then I remembered... the park is owned by Pops' father. Of course a rich father who loves his son would fill an entire house with paintings of his likeness.
Benson may avert All Drummers Are Animals, but his past as a Drummer is still extremely fitting. The strongest role of Drums in a band is as Rhythmic Percussion - keeping a beat that all the other instruments are meant to play in line with. As manager of the park, Benson's job is still to ensure that his co-workers are marching to a beat he lays out - just a far less literal one.
Benson frequently includes Mordecai in the blame even when a problem is mostly or solely Rigby's fault - however, "First Day" reveals that Rigby was too lazy to fill out a job application and only really got his job alongside Mordecai because Mordecai vouched for him. As a result, any problems that Rigby causes would naturally reflect badly on Mordecai as well.
In "Access Denied", both Mordecai and Rigby get denied access despite wearing attire that one would assume would get people into clubs. Were they kicked out because they didn't wear any proper attire, or because they have a "no shoes no pants" policy?
Throughout "Think Positive", Mordecai and Rigby are a bit more antagonistic to Benson than usual, as though they're actively trying to do their jobs wrong to make him mad, instead of just doing so by incompetence or slacking off. This can come across as just temporary Flanderization for the sake of the plot, or it could be that, since it's A Day in the Limelight for Benson, we're seeing them from his perspective.
Sure, Mordecai got a do over from Father Time after killing Rigby in "It's Time", but just the fact that the memory of violently killing the person he cares about the mos] will remain with him for all his life is just... sad; what's even worse is that Rigby will never know that his best friend killed him in an Alternate Universe.
And if that's not enough of a kick in the stomach, thanks to "House Rules", he's trapped with the knowledge that Rigby may die an unavoidable early death...Sweet Dreams, Mordecai.
It's also referenced in "Diary", where Mordecai says "Let's not put anything in the microwave..." after thinking about the first of Rigby's deaths.
Everybody remembers Susan right? Of course you do. Remember her ability to morph her subordinates into her? Well, it's quite possible that the normal looking Susan was somebody else entirely, and that she uses these "clones" to transform as many people as possible so that she may devour most of them, send one (Or maybe even a group.) to get a different job, rinse and repeat.
It's possible that the giant Susan at the end was the original Susan, and Benson was the first to rebel, allowing the Park staff to take her down once and for all.
It didn't make much sense that there were starving dogs in the park in "Death Punchies" after Rigby takes over. Then you realize that Rigby probably killed their owners.
Rigby obsessing over cakes, which he should be allergic to.
After "The Power", there is now a gigantic rampaging monster roaming the surface of the Moon... wait until NASA comes across that!
How will that wizard at the beginning will react when he finds out that someone stole his keyboard...and smashed it?
Rigby getting egged seemed pretty light compared to what happened to the rest of the gang in his Halloween story, until "Eggscellent" when we find out that Rigby is allergic to eggs. To Rigby, it is really a pretty harsh death.
In "Peeps" Peeps seems to spontaneously generate extra eyes, which doesn't seem like much until you realize he's playing to take everyone eyes. Where do you think he got those other eyes?
In "But I Have a Receipt", after Mordecai stabbed the game store manager in the chest with a ruler, the manager decides to drive home so he can lay down for a minute despite being gravely wounded. In "Exit 9B", among the people who were revived to get revenge on Mordecai and Rigby for killing them is the game store manager. The fact that he was there means that he died along the way when he was driving or at his home.
True, but if the case of the former was happening, Mordecai and Rigby would have inadvertently killed more people because of the manager death potentially causing a traffic accident and not know it; so in some form and fashion, Mordecai and Rigby can come off as a more-or-less Deconstructive Parody of the Karma Houdini pair at their worst.
To be fair, the store manage was trying to kill them first, so he's no more or less deserving of death than their other enemies. Particularly since the portal was apparently to Hell.
The Death Sandwich.
In Stick Hockey, Rigby tells Benson the stick hockey game is 'to the death'. Seems like an innocent joke but then you realize: how exactly did Mordecai and Rigby make it to the finals...?
Then again they may have not killed that many people.
While RGB2 was only resting at the end of "That's My Television", the fact that he run out of 80's Air means he's gonna die eventually.
Gets worse when you remember that RGB2 is actually a human being living in a television for a long time, similar to Failure Cresh albeit a character; therefore; is slavery still legal...?!
Possibly. Keep in mind that Mordecai and Rigby were genuinely shocked to find out that he was a human being ad not a sentient TV. It's possible that the TV company have been passing him off as a sentient TV for years, so nobody would know they were violating human rights.
RGB2 defeats his evil manager and his goons by launching his bag of "80's air" at them, which then explodes in a cloud of mist and knocks the heroes' getaway van onto a passing boat. A clean way to get rid of the villain, until you realize the damage compressed air can cause skin and internal organs, even blow one's eyeballs out. And this CEO had cans of it burst in his face. It probably wasn't pretty when the mist on the bridge cleared.
In "Limousine Lunchtime", Skips claims that Mr. Mallard loves his limo almost more than his own son Pops... and at the end after he stains the seat of his recently restored limo, he claims he's so rich he can just buy another limo... does anyone find this messed up?
Stress in the Regular Show world can kill anyone, even immortals.
In Every Meat Burrito, Mordecai, Rigby, Muscle Man and HFG want to eat burritos with meat of every animal. Most likely including birds and raccoons. The ending implies that the Every Meat part is just chicken, but still, Mordecai and Rigby didn't know that. And since it's not confirmed if it was every meat, they could have unknowingly eat another member of their species.
Thomas in a pizza costume in the main continuity. Now the reason why he's forced to wear the costume till Thanksgiving dinner is because he lost in a scary story telling contest, now that "Terror Tales from the Park III" is canon due to Thomas in the pizza costume... THAT MEANS JEBEDIAH TOWNHOUSE IS REAL!
How many people drowned when Benson's apartment submerged in "Saving Time"? All because of a 'harmless prank'!
Natalia the Russian spy from "The Real Thomas" falls out of her helicopter and into the gaping maw of a passing whale. Except she was swallowed whole, meaning she likely didn't die and was trapped in the whale's stomach, slowly being suffocated and digested alive over the course of several days. Another random villain death that becomes much more harsh when you stop and think about it.
Margaret's "boyfriend of the week" Angel from "Mordecai and the Rigbys" was seen in the Rock Star underworld in "Guitar of Rock". Meaning Angel is the only boyfriend Margaret had that died.
During Skips' flashback to the night, prom night to be specific, that Desdemona died the song they shared a dance to foreshadows what is to come. [The song was Forever Young by Alphaville, the line "let us die young or let us live forever" comes true with Mona dying young while Skips became immortal thus living forever.
In the episode "Brain Eraser," Mordecai sees Pops naked. Pops, in a panic, covers his crotch with his top hat. But when he removes his hands, the hat stays in place. Rigby's gesture with his pinkie also gives a good idea as to what Mordecai saw. Not only did Mordecai see Pops in the nude, he saw Pops with an erection. No wonder Mordecai was so haunted by this.
The people of Lolliland happily inform the crew that everything, even them visiting their museum, has happened in previous universes. In one of the tapestries even Eileen is there, (meaning she was always destined to go to space) and they're wearing battle armor, so this same scenario has played out differently. And in every other timeline, Pops and Anti-Pops' battle led to the death and rebirth of the universe. Which in turn means Pops has witnessed his friends fail and die potentially billions of times, and was only able to end the cycle by destroying himself along with his brother.
As mentioned, the park house is filled with portraits of Pops, mostly of him looking happy/goofy. In the finale, Pops dies. All of the park crew came home to the park house to find it filled with pictures of their recently deceased, VERY dear friend. Those must have been fairly hard to look at upon their return.