All There in the Manual: Details about specific moves, events, and characters not mentioned in show can be found in the Bios posted on Tigura's Deviant Art page.
Anachronic Order: The prequel series Raccanto are released in nonsequential files. So far it's 12, 1, 2, 6, 8, 5.
Aura Vision: Lucario, much like his game counterpart. Bowser's Aura reinforces Lucario's hostility towards him despite being the reincarnation of Mewtwo, Bowser's friend and fighting mentor in Melee. Later subverted by Fox, who judges people by looking into their eyes. What Lucario sees with 'just plain sight' contradicts Bowser's aura, leading to his Heel-Face Turn. However, at the end of episode 13, it turns out there may have been merit to said aura.
Deconstruction: Has some elements of this, especially with Link on how the pressure of being a designated hero can really turn for the worse.
Word of God says this was an overarching theme of the series, and how it works especially well with Link. Also a subtle Take That to the other machinima cliches, particularly how Link's ALWAYS the hero, ALWAYS saves Zelda, and ALWAYS beats Ganondorf.
Doing It for the Art: Machinima is never made with profit in mind. Tigura21 also refuses to put Smash King on Machinima.com's YouTube channel, pretty much the only way to actually make money with machinima, due to not wanting to lower the quality of the series by adhering to Machinima.com's rules.
Easter Egg: Jigglypuff is occasionally seen sleeping somewhere within the world of Brawl, and each episode has one sighting of the Balloon Pokemon. Word of God says the "Jigglypuff Sighting" is like a game of Where's Waldo? and are subliminal messages like what Smashtasm has.
Gone Horribly Wrong: Bowser was meant to be contained and de-energized from one of Samus' shots. What it really did was give him so much power he was almost immobile... so he resorted to turning into Giga Bowser, which extended his Ascend Form to THAT as well.
Hidden Depths: Lots of characters have this, but Link is probably the most memorable.
Dedede is shown to be perverse, and a bit of a womanizer... But he's also fairly good-hearted, and incredibly perceptive, going into detail about Bowser's fight with Donkey Kong.
Imagine Spot: Captain Falcon has two of these considering possible outcomes on who wins the race. If he wins, Sonic wears a Falcon uniform and becomes his number two. If Sonic wins, Falcon wears a Sonic uniform and be forced to lick off his shoes like a slave. Sonic is disturbed by both of these.
Sonic: Don't you have any pride for yourself? Or me? ESPECIALLY ME?
Episode 15 has Wario and Squirtle have one each as well, centered around Bowser. Wario's being Bowser ruling a post-apocalyptic version of Brawl like a tyrant, while Squirtle's is a very cute childish story of him breaking out of his prison and beating up the B.S. Society, minus Pit, before making his escape.
Knight of Cerebus: Ganondorf. Every single time he appears, everything starts to go to hell.
Link as well. Aside from Ganondorf, he became very violent and murderous due to being tired of always being the hero that everyone envsions. And at that point caused the death of one of the characters.
Legacy Character: Technically the entire cast. Everyone with the possible exceptions of The Creator, Midna, and Shadow is a reincarnation of the specific character they were based on, and are reborn anew when the current incarnation loses his/her 10 life stock.
There was a Time Skip after Episode 8, so it would make sense that guys like Ganondorf and Bowser learned a few tricks. Mario's potential also doubled due to a particular sticker given by Roy.
Noodle Incident: Wario is never allowed to use Bowser's bathroom again. We probably don't need to think too hard on that.
Out-of-Character Alert: Sort of a subversion; Mario, upon meeting Wario and Meta Knight (and realizing one of him is Bowser's teammates), insists he is a friend of Bowser and needs to take him to Bowser's home to see him. Since they never met prior, they took his warning of Ganondorf at face value. However, Meta Knight caught on the slip-up that he's a friend of Bowser's, yet doesn't know where he lives.
Power Trio: All contestents in the Smash King Tournament are set up into three man teams.
The Creator's Triune, consisting of Bowser, Ganondorf and Mewtwo, who were created to be challenges to the other Smashers to help them evolve, and thus were given different attributes for this goal. This is the reason they are so mistreated aswell, as these qualities among other things made the other Smashers start to dub them as villains.
Bowser: You think I don't know? You think I'm not aware of my position here? Why you're so fixed on getting me under your control? Why you keep calling me your "pet"? Your goal is beyond you. You can't do it without me. Every pretty word, every twisted lie, everything you do is related to me. Because you're too weak-no, no-limited to do it all on your own. But, want to know what's funny about that? You can't do anything about it, even if you wanted to, even with the great powers you have now. You're still the same as you ever were, and always will be...number two.
He gives a two-for-one speech in Racconto File 6 To Mario for spoiling Peach and Peach for wasting her potential.
Reincarnation: It has been implied that some characters, like Bowser, are actually different from their previous selves over the time of being trophies.
The Remake: Tigura21 has already remade a few earlier episodes of Smash King. He wanted to fix some of the errors he made before, clear a few unexplained points up, film the scenes in HD, as well as add the new intro and outro. Only episodes 1-7 wil be remade.
Reset Button: Anyone who exhausts their 10 Life Stock is reincarnated as a blank slate of their original character. All memories and experiences built up are erased.
The Reveal: The group consisting of Zelda, Snake, Samus, and Wolf was hired by the Creator to capture Bowser, and take him to Him. Bowser, along with Ganondorf and Mewtwo/ Lucario, is one of the Creator's Triune, three beings the Creator made to challenge the other trophies. As a result, the members of the Triune evolve and grow faster than the others, Bowser especially. To this end, Bowser could become as powerful as the Creator. Ganondorf seeks to use Bowser to overthrow the Creator, and remake the world as he sees fit.
Running Gag: Mario and Bowser manage to keep missing and passing each other, even when they're on the same stage. Until Episode 13 that is.
Schedule Slip: The Reunion Special, Christmas Special, The double episode release.
Speaks Fluent Animal: Since Liz doesn't know English, her speech is usually roars. Pokemon, Bowser, and Wolf however can understand her perfectly.
Throw It In: That scene with Captain Falcon tripping in the first episode? The creator decided that it worked so well, he kept it.
There were also the beat-up scenes of Bowser->Wario and Zelda->Dedede, completely ad-lipped. Zelda's was completely unintentional but Tigura liked it so much he added it on, with Dedede's own cries of pain to boot.
Time Skip: Nearly a month has passed between episodes 8 and 9.