Alternative Character Interpretation: invoked Seen to various degrees, but most prominent with Roronoa Zoro as played by Cory: he's a Half-Human Hybrid whose insane strength is explained by his being 1/16 Giant and 1/16 Fishman. All of his quirks are linked to character Flaws, and his Undying Loyalty? Another Flaw Cory accidently triggered when he promised to follow Luffy.
Bad Bad Acting: Luke and Cory's attempts to roleplay for extra experience tend to fall into this, especially early on.
Badass Adorable: Makino, the bartender from Luffy's flashback with Shanks, when the bandit comes in and starts breaking stuff. The GM had earlier threatened to call up the old "bartender is really a very high-level retired badass fighter" should the players start another bar brawl. Even more fun since the whole scene is played out by Luke alone (acting for everyone involved), so he basically invoked the GM's threat on himself.
Badass Normal: Nami may not be as statted out as Luffy and Zoro, but she's still able to pull off stunts that make Luke go "Holy crap, that's badass."
The GM has implied that Coby will become important in the future, as Cory's decision to consciously abandon him will "bite [the party] in the ass."
Crossover: With Friendship is Dragons, wherein Applejack's player is revealed to be another of Cory's cousins, and he, Luke and Nat try designing their own characters for the pony campaign. Starts here.
Continued here in a second mini-arc, with Rika getting into the act.
Distracted by the Sexy: The GM's roommate Phil, a non-gamer who had been avoiding the group prior to his introduction, suddenly stops in his tracks and considers joining in when he finds out there are three girls in the group.
Dope Slap: Natalie gives the GM one during the Syrup Village arc after he takes far too much pleasure tormenting new player Phil.
Drop The Cow: Luke once attempted to launch a cow at his enemies during a The Tower of Druaga RP. It got them TPK'd in their first battle, and his old group promptly kicked him out afterwards.
Epic Fail: Invoked intentionally. Luke has a d20 with nothing but 1 on it, and uses it whenever Luffy has to make some kind of social skills check.
Exact Words: After being told he could play his Minmaxed-out-the-wazoo character concept only if he provided a name and background, Cory named his character Roronoa Zoro. After all, the GM must have made a backstory for this obviously important and already-named NPC, right?
Failed a Spot Check: DM's reaction when the three kids jump out of hiding to beat her character up lampshades this.
DM: Seriously? None of us noticed them? These kids must be ninjas.
Faking the Dead: This was Captain Kuro's plan: the real Captain Kuro had Jango hypnotize Kurahadol to believe he was the pirate so that he could be executed in his place. However, Kuro died before the job could be finished, and Kurahadol inadventantly gained his powers through his belief that he was really Captain Kuro.
Fantasy Gun Control: Aside from the special equipment powerful villains may carry, most guns are weak and unreliable flintlock designs, with rounded bludgeoning bullets (thus allowing Luke to apply his damage reduction) that do damage. Phil complains about his character carrying a slingshot, but it may be significantly more powerful than regular firearms.
The Syrup Arc confirmed the latter when Usopp got shot... for a measely 4 damage.
Flaw Exploitation: The GM is a master of this when it comes to the characters' in-game Flaws. He's also able to pull this on the players themselves at times.
After Ganzack supposedly kills Medaka, Rika says she has an idea for a medic as her next character, suggesting she's going to play Chopper or Kaya down the line. Sure enough, once they reach Syrup...
Coby has a Fatal Flaw which can cause him to freeze up in combat situations. The GM gave a very similiar flaw to Usopp, having designed both characters as NPCs.
Cory's insistence on constantly checking for traps makes more sense when it's revealed their former gamemaster was a killer one.
The "Syrup Village" arc is practically dripping with foreshadowing for Phil/Usopp and DM/Kurahadol.
When Luke mentions Luffy's straw hat and that he's named "Monkey D." (which he shamelessly stole from an NPC in the sourcebook), the GM starts scribbling in his notes, implying that Luke may accidently made himself more important to the main plot.
Before DM leaves near the end of the Syrup Village arc, she and GM have a chat, and she finds his dropped notes for a GMPC.
Friendly Enemy: Even after it's clear their characters won't be able to get along, Luke and DM trade compliments and comments about their character builds and such while fighting. (Up until Luke realizes DM never intended to join their party, at least.)
Half-Human Hybrids: To justify Zoro's insane Strength, Cory created him as 1/16th Fishman, 1/16th Giant.
Helmets Are Hardly Heroic: During the Devil's Tower arc, the GM figures that since helmets don't add to your Armor Class, Medaka is only wearing one to hide something about her character. She promptly accuses him of metagaming.
Humiliation Conga: Phil (and Usopp's) introduction to the group, where he misreads the GM's handwriting and thinks his character's got more resources than he actually does, the others take advantage of his not knowing the rules — and his first dice roll? Natural 1.
Hypocritical Humor: When Medaka accuses the GM of metagaming, he casually asks her about a random monster. She immediately rattles off all of its stats.
When Phil/Usopp successfully bluffs the Usopp Pirates into taking Kaya to safety, DM snidely comments on all the effort he put into ordering around three NPCs. She then spends the following strip ordering Jango to follow them.
I Know You Know I Know: Luke and Natalie engage in some back and forth thievery over the same map, escalating it in this manner.
...enough that Cory misreads his Knowledge Check about Roronoa Zoro.
Later, he has to resort to texting Natalie when she tries to make Knowledge Checks about what Cabaji's saying.
Phil initally misreads his character sheet and honestly thinks Usopp has 8,000,000 followers instead of three nine-year olds.
In and Out of Character: Used regularly in the series. The GM is used to this, to the point of being shocked when they manage to stay in-character.
Innocent Innuendo: Used by the GM to force Cory to read Zoro's Backstory: without it providing much-needed context, Helmeppo's comments about his endurance and "dropping by again for our usual bit of fun" sound... well...
Interface Spoiler: While other characters have been played by the main cast, only the actual Straw Hats get character stat sheets.
Internal Reveal: Since the GM designed Usopp as an NPC before giving him to Phil, Phil doesn't know anything about his character. Thus, he doesn't understand why the GM keeps smiling when he brings up things like warning the villagers about the immenient pirate attack...
Ironic Echo: When Natalie first introduces Nami, the GM's stunned at how much work she put into her character, comparing it to a small novel. Much later on, Rika comments on the amount he apparently wrote about Usopp:
Rika: I can't believe you handwrote 50 pages worth of backstory.
Funny thing is? He didn't. A good portion of that is actually random campaign notes that got mixed in somehow.
When Usopp punches Kurahadol, the GM tells Phil he doesn't actually have to punch DM. Phil snaps "I know that!" and is outraged by the suggestion. Later, when Kaya slaps Usopp, the GM offers her extra roleplaying XP if she slaps Phil for real.
Jerk Justifications: DM uses Type 3 to justify Kurahadol being a massive prick to everyone: that's just his IC attitude, and she's keeping in-character, even if that rubs everyone else the wrong way both in and OOC.
Kick the Dog: Discussed when Helmeppo bullies the little girl Rika:
Cory: Okay! We get it! He's the bad guy! Sheesh, man! GM: Pfft, with you guys I can't be too subtle. Now watch him kick around this puppy.
Killer Game Master: He's the one who taught Luke how to min-max in the first place, after all. And he just loves playing to the cast's many flaws.
Their former GM, DM, was even worse about this. Cory apparently learned to obsessively check for traps the hard way.
Line-of-Sight Name: Played with: after arguing about the validity of his first character design, the GM told Cory he could play him if he first came up with a name and character background. Then Coby gets his first look at Roronoa Zoro...
Mood Whiplash: Deliberately Played for Laughs with Medaka's Heroic Sacrifice. Several rapid-fire jokes occur right beforehand, the GM apologizes, Luffy apologizes to the player... and then Rika starts cheerfully working on generating her next character while telling Luke to make sure her new one gets all her old character's stuff.
The Munchkin: Cory (Zoro) and Luke (Luffy). In the former's case, it got his initial character attempt briefly banned from the game. Given that the GM designed parts of the game with this in mind, this makes Natalie's life rather difficult.
My Name Is Not Zero: Luke has trouble keeping Zoro's name straight when they're first looking for him.
Mythology Gag: A couple of the questionable edits from the 4Kids dub get turned into wacky ideas the GM came up with.
Name's the Same: The little girl who gives Zoro riceballs is named Rika. That also happens to be the name of Cory's cousin, who calls during the Orange Town arc.
No One Could Survive That: Natalie deliberately invokes this during the fight with Buggy so that they can have the 'grand final confrontation' the boys were itching for.
Invoked by Luke later during the Syrup Village arc to avoid getting killed off by Kuro and Jango while he's asleep.
Noob: Phil, the GM's roommate, never tried the game before. Thus, when he impulsively decides to try it out, the GM gives him the pre-designed NPC Usopp to play with, and he doesn't understand any of the terminology or what's going on. He is, however, picking up the roleplaying aspect of the game very quickly.
Noodle Incident: Whatever happened to the GM's 'Mythical Sea Creatures' supplement in the past, he's still bitter over it when they start their latest campaign.
Apparently, Phil also did something to the GM's car that he's still holding a grudge about. The similarity is Lampshaded:
Luke: That means you're one of us now!
Also, whatever happened during the New Year's session involving the GM, Cory, and an enormous amount of liquor.
Sadly, the GM interrupts story time before Phil tells us what happened when he mixed up his Chem and Home Ec notes. We do find some details a few strips later.
Phil: We had to evacuate the Chem lab ASAP! Rika: Hahahaha! And then?! And then?! Phil: We made more jello shots for everyone.
Off the Rails: From the moment he hears there's pirates in this setting, Luke immediately starts trying to derail the campaign, with Cory's support.
Overshadowed by Awesome: The hypnotist Jango is supposed to be the final boss of his arc, and is a legitimate threat by himself. However, Luke and Cory are far, far more worried about the fact that they also have to face DM's character in that battle.
Railroading: Discussed at the start of the Syrup Village arc: Cory tells Natalie not to even bother considering checking out any of the other islands first, as the GM will just find some way to divert them where he wants them to go.
During the Buggy arc, we get this bit:
GM: Let's see... when we left off with Nami, she was being chased by Buggy's pirates. Right now, you're positioned right above them, so... <Rolls> Cory! Stop making train noises!
Luke: Well that seems awfully convenient.
Reading the Stage Directions Out Loud: When the GM messages him to try and get Usopp to sneak off and see Kaya without letting the Straw Hats know, Phil promptly tells them he's not supposed to let them know where he's going.
Retcon: In-universe during the Devil's Tower Arc: After discovering that Medaka didn't die, the GM pulls this by announcing that the bonus Luffy got after witnessing her death doesn't apply, meaning Ganzack lived through his vengeful attack after all.
Luke and Cory played Rock Lee and Gaara in a Naruto fighting game.
Luke, Cory and Nat sat in on a session of Friendship is Dragons and tried creating their own characters for that setting. A later crossover led to them trying to pick up a game back home, with Rika getting involved.
And they played at least three sessions of a Spy Drama. Luke got his first character killed off quickly and played Chuck.
Strange Minds Think Alike: Upon realising that Usopp has a retractable grappling hook, Luke, Cory, and Phil all start singing the Batman theme song.
Take That: Unsurprisingly, the 4Kids version is mocked.
Undying Loyalty: Zoro, to Luffy, thanks to a very serious flaw he took with the full intention of loopholing his way out of... until joining Luffy's crew as a subordinate, thus putting it into full effect. While the specifics are as yet unmentioned, it's implied that letting Luffy die before him or even letting him down in any way will have dire consequences.