Mike giving Celia a promotion to floor supervisor isn't just a simple act of playing favorites; all that time Celia spent as the company receptionist meant that she would have had plenty of opportunity to study the ins and outs of the basic day-to-day operations and then some. And since Mike knows his girlfriend quite well, he knows that she's capable—and her being the Laugh Floor F Supervisor has proven she's got the skill to run a smooth operation (well, as smooth as the transitioning company can get).
Plus, Mike knows a thing or two about working hard to try and move up in the company, and wanted Celia to have that opportunity as well.
Why would the company board of directors put Mike and Sulley in charge of Monsters, Inc. when they have no experience running the business? It could go a multitude of ways:
Mike and Sulley's names are amongst the top in the scaring business. If they not only discovered an alternate form of energy, but encouraged the public to embrace it, it would make a lot of customers and potential employees a lot more willing to embrace it. This ultimately does happen, since the company not only ends the energy crisis, but it creates a much happier working environment—the ultimate incentive to get people to join them.
Mike and Sulley were the ones that exposed Waternoose’s corruption. While most of Monstropolis may seem them as heroes for this, adding to their aforementioned popularity, it also makes them responsible for the current situation. Added to the fact that switching to Laugh Energy is implied to have been Sulley’s idea in the first place, and the prolonged interaction he and Mike had with Boo, it makes sense to have them be the ones leading M.I. through this transitional period.
If all else fails, they can both be The Scapegoat and the board can wash their hands of them like they did Waternoose when his failings were exposed. Obviously this doesn't happen, but seeing as neither monster had experience in business, the board could easily use that as a means to get rid of them should things get worse.
There’s also the fact that they started from the bottom up as shown in Monsters Unviersity. They have knowledge and experience with most of the lower ranks of the company compared to a regular board member who started comparatively higher up the ladder. They also likely have friends within each of those divisions who are more likely to get along with the new bosses and keep productivity up.
Which brings us to the next point: The company is in need of a “popular friendly face” after a scandal like Waternoose’s. Even putting aside any possible friends within the company, James P Sullivan alone is a monster of well renown, to the extent two CDA agents ask him for an autograph.
Most Jokesters seem to have a "thing" that they stick to in their comedy, like Carla's spitting flower or Lanky's spinny tie. These things would get old and unfunny pretty quickly...if they visited the same kids every night. Unlike in the original movie, there's no indication the Jokesters are assigned to specific kids—that means an eternally rotating audience roster, and thus the material appearing much fresher and funnier to each new kid.
Come to think of it, this might be why the designated monster thing was done away with. Things that scare someone are going to keep scaring them time and time again, especially in the case of phobias (the dark, spiders, etc). Comedy, on the other hand, works partially on the principle of surprise—if someone isn't expecting a punchline, they're more likely to laugh. It's why jokes stop being funny after you hear them once: the surprise is gone.
Mike is running himself ragged going through door after door gathering laugh power. Part of the reason is because the power crisis is still a problem and they need every capable monster. Another reason is because it's been Mike's dream to work as a Scarer, but it was deemed impossible. Now that laughs is the main source, Mike has the opportunity to live out his dream in a sense other than being a coach, and is making up for lost time.
Another thing to note is the canisters. They are still using the canisters for scaring, while the ones in the movie’s epilogue are much bigger due to laughter being far more powerful. They could be obtaining the same amount of laughter in fewer trips by upgrading the canisters, but have not realized this yet.
Mike taking care of Snore rather than have Sulley do it may have different connotations than simply trying to prove he can do it without actually "caring". It may have only been a few hours since she was sent back home, and Sulley has other things to worry about (like running an entire company for instance), but as the finale scenes of the movie show, the big guy still misses Boo terribly. Having to take care of another human kid (albeit under more pleasant circumstances) could have brought up a tender subject for him, so Mike was likely trying to spare Sulley from having to miss her. Notice that Mike only brings up the Boo incident once, and Sulley seems to be having a bit of an awkward time dealing with Snore while at the baseball game? He may not admit it now, but he's still heartbroken about having to say goodbye to Boo.
As an addendum to the top entry, Mike was the only perfect candidate to take care of the child. He was not scary by any means, and even kids at a camp ground thought him cute. If Snore (the name Mike gives the baby) did became a problem, Mike could easily calm her down because it's his natural gift to cheer kids up.
Roy "Big Red" O'Growlahan working as a sportscaster is no surprise, considering that Jaws Theta Chi was made up almost entirely of Jerk Jocks (except for poor George).
Why does Roze tell all the jokesters who are being evacuated from Laugh Floor F after the Code 418 that it doesn't mean they get the rest of the day off? Remember that Smitty thought Waternoose getting arrested meant everyone got the rest of the day off, which Needleman has to remind him that such an arrest was going to get the factory shut down (at least until the laugh power idea came around). Considering how chaotic the transition to laugh power has been so far, it's not hard to imagine the monsters did take the day off when Waternoose got carted away, and Roze, being the sister of the one who carted Waternoose away, wasn't going to let that happen under her watch.
There is a possible reason why Roze is so lenient with Gary's lack of paperwork. Unlike Mike, we don't know really know if Gary shares his habit of not doing paperwork on time, for all we know, it's just a first time offense for him. Not to mention he already seems like good friends with her, so of course she would cut him some slack.
Needleman and Smitty are shown to have saved doors from being shredded when they present a variety of options for Fritz to vacation in, in spite of it being against company policy. It serves as a clever hint towards how Mike managed to reassemble Boo's door at the end of the movie, since they would have likely saved the pieces from that day's shreddings so Mike could dig through it and put it back together.
That raises a question. Why didn't Sulley and Mike lift that policy? Aside from Mike accidentally revealing one of those doors was in their office, the policy makes Sulley look like a hypocrite for reassembling Boo's door.
The monster world still believes humans are toxic. Panic could ensue as a result of the policy being lifted.
Adorable being banished for learning about the Scream Extractor like Mike and Sully were makes sense. The number of locations that a monster could be banished to- being 'remote' enough that there's little human contact- is fairly low, especially with humans all over the globe by the present day, so the options Waternoose had to pick from to get rid of those who found out about the machine was already low enough that he had limited options to choose from. Waternoose already got rid of one person who knew about the machine through the same banishment door, so it makes sense he'd re-use the same one to get rid of Mike and Sully when they learned about it as well, hence, though they never knew it, they were all banished for the same reason.
Of course Waternoose wouldn't hesitate to hire Tylor when the time came. Sulley would've had to keep him updated on the boy's progress, and his record would be enough to convince Waternoose that he's the company's ticket out of the energy crisis, thus he was desperate enough to hire him immediately.
Roz working under M.E.R.C. makes a lot of sense as she would have the power to directly investigate companies without needing to go undercover. Remember, she failed to detect Waternoose's corruption during the two and a half years she worked at his company, and then failed again when the CDA agents missed the Scream Extractor while they were combing over the place for Boo. Needless to say, Roz is probably not messing around anymore and she's going to turn whatever suspicious facility she finds upside-down to prevent another incident.
Overlaps with Fridge Sadness, but the reason Tylor is so guilt ridden for turning down Johnny's offer in Season 2, especially after he learns that his family is bankrupt, is because (according to a deleted scene) that they saved every penny they had to put him through college. Now that he's graduated and ended up in a far different position than what he went to school for, he probably feels very guilty for making them waste all their money like that.
Johnny being like Waternoose is fitting since Johnny is not only willing to keep Scare Power running by, he's willing to cross lines to keep the public view of it and his company going. He's willing to work with Randall to ensure it's success and has a similar break down when being arrested towards the top scarer too. Even more fitting, his prison cellmate just happened to be Waternoose as well. The difference the two is a lot less noble in a sense, Johnny did it completely out of spite because he felt that Mike and Sulley deserved as much from their college days. Waternoose did what he did because he was genuinely scared for not only his company going out of business, but for Monstropolis as well, due to the growing energy crisis and the pressure had gotten to him.
Tylor's jealousy towards Val becoming a Jokester is also similar to that of Randall in a sense. Randall had to witness Sulley and Mike achieve success greater than him despite them being college drop outs, while he had gotten a proper education and training. Tylor had to not only get his education, top of his class no less, but had to relearn a new profession on the fly because what he learned wouldn't apply to laugh power. Val showing him up, unintentionally, struck a cord with him because he had to work double as hard to simply get where he is, Val's natural talent let her skip all that, which damaged their relationship a bit. The difference is Tylor managing to get over his jealousy and congratulate Val for her new position, Randall wasn't about to let that happen with his festered emotions.
Tylor and Val were the perfect duo to show off Laugh Power than Mike and Sulley did in their presentation. While by no means impossible for the duo, Mike and Sulley were tethered to trying to sell Laugh Power as a business, which wasn't likely to happen since Monsters, Inc. has such a poor reputation now due to the switch, not to mention the two lack the experience in business to begin with, they are essentially trying to sell the idea on their words alone. Tylor and Val are two young monsters that are participating in the practice, showing a live demonstration of it no less. Not only that, they witnessed Tylor's humility by apologizing to Ben for scaring him and the three of them having the time of their lives. They demonstrated why laugh power is better by showing the masses that it's not only safer for all parties, it's morally better.
How and Why does MIFT even have the Scream Extractor on hand to begin with? Wouldn't the CDA or MERC want possession of evidence? It could be because it never came up. The CDA only got Waternoose on confession about kidnapping children, while Randall was unofficially banished and Fungus was forgiven for forcibly taken part, they had their hands full. It's more than likely that Mike and Sulley told them about the Scream Extractor, but it's entirely possible it wasn't needed anymore since Waternoose's conviction was all but assured and were simply asked to dismantle it, and of course they asked MIFT to do so.
It was also poetic for Roger to be able to use his Father's diabolical machine to save the day and prove he's not one bit the man his father was as well.
With the revelation that Johnny had been committing morally dubious acts behind everyone's back, Roz's warning to Sulley and Mike last season that they had to step up their game or else lose business to Fear Co. takes on a much darker context; Johnny no doubt heard about M.I.'s switch and was probably planning his scheme right from the get-go in case they succeeded in making laugh power take off, and Chet would have already been imbedded in the company as The Mole. Roz wasn't just telling Mike and Sulley that they had to generate the necessary power in a day—she was warning them that there was another Waternoose in the works, and that if they failed, the two would be handing the city over to him.
The seventh episode, Adorable Returns, reveals that the temperature in the Monster World can go up to 251 degrees and have 140% humidity. This inadvertently adds more reasons on why humans are not allowed there if they're not really toxic to monsters. This world is hazardous, if not outright fatal for human beings if they stay too long. Good thing Boo and Snore were brought into their midst on cooler days...
This would explain how Sully, and more importantly Mike, were able to survive the blizzard in Nepal and return to their world. They know how to deal with extreme weather conditions. Sure, a blizzard could still be deadly, but they stood better chances than any human being would.
Sulley's gotta shave...
This episode also frighteningly reveals that people in high positions in the Scare companies can just banish people with no repercussions, as Waternoose just did it with Adorable, Sulley and Mike. Who knows how many other monsters were banished on a whim.
In the Cold Open of Little Monsters, Tylor's seventh failed audition has him accidentally set the dummy on fire. The scene is played for laughs, but imagine if that happened to an actual child. No wonder Ms. Flint is so quick to end his auditions...
Tylor accidentally mixes up laughter and scream energy together in the same canister, which nearly causes a massive explosion at the C.R.E.E.P. convention. That's terrifying enough, but given Needleman and Smitty's nonchalant reaction to the situation, it makes one wonder how many times this energy has gotten mixed up because someone didn't bother to clean the can. Worse yet, it would explain the terrible destruction wrought by the Unversed during Kingdom Hearts III when they attacked the factory and started scaring children for Randall; all that scream energy had gotten into the unfilled laugh canisters and began creating literal bombs that started the fire seen partway through the level. Thank God Sora and the others were there, because the whole plant could have gone up in a crater.
During "Field of Screams", Chet mistakenly believes that he's killed "Stubby" Lizzardo. Stubby's fine, but Chet implies this isn't the first time he's accidentally killed someone before...
While M.I. is scrambling to get enough power for the day, Mike is dousing himself with as much 36 and 1/2 hour energy drinks he can to keep going. It's funny to see him back in full energy mode, but he's guzzling so much down, that has to be bad for his heart.
A scary thought is that, Randall infiltrating Monsters Inc. would suggest that he would know what would happen if laugh and scream power is mixed together, but he still went ahead with Johnny's plan. Either he did his own research like Johnny said they did, or he was so blinded with petty revenge against Mike and Sully that he simply didn't care and went along with the plan, just how low has Randall sunk?
