In "Stupid Mario Party", Kermit tells the group to "chill while I try and murder you guys". The winner (Yoshi) was the one which stood perfectly still throughout while everyone else ran around, he was the only one who just chilled.
"Stupid Mario Kart" - the karts that everyone uses all make an amount of sense, given how the characters are portrayed.
Mario - Standard Kart: Too retarded to process anything more intricate than the basics.
Luigi - Super Blooper: No one takes him seriously, and it's kinda deserved.
Waluigi - Offroader: Throughout the entire episode, he plays dirty.
Even the fact that SMG4 is in Lakitu's cloud is fitting, as he's above this complete nonsense.
In "Super Backwards Bros.", the twist that the episode is based on one of Bowser's fanfictions makes the character swaps perfect.
Bowser as Peach and Peach as Mario will allow the two to hook up while leaving Mario as Bowser to get beaten and humiliated. Surprisingly well thought out for an SMG4 video.
Following that, Bowser's decision to make Toad Luigi makes sense, when "Meet The Toad" showed they sometimes hang out together. However, there's also the rather strong implication that Toad arranges some of the kidnappings of Peach. What does he gain from this? Well, with Peach taken by Bowser, no one bosses or mistreats him and the other Toads (except for Mario himself) for quite a while. Which was also revealed in "Meet the Toad".
Luigi-Toad is, however, shown to be rather reluctant to save Princess Bowser, also insulting Bowser a few times. Bowser and Toad may be part-time buds, but Bowser is still aware of Toad's actual nature.
In "Detective Mario & Pikachu", the twist that Mario stole the statue is excellently foreshadowed.
At the beginning, Mario was in the basement. He says he "also couldn't believe there was some spaghetti down there". Note he said "also" - he was hiding the statue as well.
Mario following and being stupid around Detective Pikachu throughout the video - the "Pokémon battle", eating the ice cream and stating Pikachu told him to, rifling through the trash; all things Mario does regularly. Except not: he's really doing it to sabotage the detective while pinning the blame on someone else.
Mario playing detective. Both times, he finds evidence that leads to someone else being the perpetrator. The first leads Det. Pikachu to the Wario Bros. The second leads them to Luigi, him having delivered the evidence to the Wario Bros. Mario was trying to frame both parties.
The above gets some extra brilliance - both parties have motives. The Wario Bros have committed crimes before and have something to hide, so they are likely to have stolen the statue. Likewise, Luigi mentioned having to pay damages caused by Mario, and what better way than to sell a statue for money?
Mario having "solved cases before". Naturally, he pegs SMG4 as the culprit because he beat Mario in Smash. This turns out to be Mario's motive for stealing Bowser's statue.
Mario goes to find ice cream in the back of the truck, despite having eaten Luigi's stock. It was so he could call Toad to stop Det. Pikachu from finding out Mario had given the package to Luigi - thus finding out Mario had stolen the statue.
Look at Mario in the scene when Toad is caught - he jumps around in surprise, then shakes his head at Toad to stop Toad from ratting him out.
Waluigi's Power Of Rejection. Pretty fitting for the literally-translated "Bad Luigi" to have an evil version of Negative Zone.
As the T-Pose Virus is analogous to a zombie apocalypse, it makes sense that the undead could be cured with extra lives.
In the "Mario and the T-Pose Virus" episode, it might seem kind of weird that a 1-Up can explode into a green cloud until you remember that mushrooms reproduce through spores.
In "War of the Fat Italians 2018", Wario goes on a long, arduous journey just so he can find a therapist for Waluigi. Why does it take him so long? Well, this is the SMG4 Universewe're talking about. Finding a professional capable of solving Wario's family issues un-ironically is like finding a needle in a massive haystack. That and/or all the good ones were hit with the T-Pose Virus.
Boopkins did not actually put on weight in between "The Mario Purge" and "Mario And... The Well". The reason he didn't float was because the water in the fire truck was in fact vodka. Also, the reason the policemen "drowned" was due to alcohol poisoning.
It might seem odd that SMG4 chose to release the 3M Collab during the Anime Arc instead of waiting until it's all over, since Meggy has been shown in the thumbnail completely fine when she's supposed to be kidnapped... until you realize that Meggy has been turned into a human, and SMG4 wanted to keep this form a surprise.
Saiko from Doki Doki Mario Club should consider herself lucky that her relationship with Fishy Boopkins ended the way it did, because it's not very likely hisdad would be too pleased with her behavior...
That being said, she does have a minor breakdown in The Mario Convention once reminded of the above incident, and Fishy asking her to watch anime scares her, as proven in War of the Fat Italians 2018. What else did they watch offscreen?
It's mentioned by Bob in "The Mario Carnival" that Wario mysteriously vanished after the events of "Waluigi's Time". This gets very creepy once you realize that "Waluigi's Time" is where Waluigi gains extraordinary powers. Did Wario get killed by The Power Of Rejection?
Thankfully proven false once the episode of Mario the Scam Artist came out.
Meggy says in "Meggy's Bootcamp" that she's afraid of driving her friends away with her obsession of winning Splatfest. Is that why we don't see Meggy's team from "If Mario Was In...Splatoon"? Has Meggy driven them away?