The Eliacube. Nox planned to use it to boost his time-manipulation powers and travel back 200 years. And when Yugo gets his hands on the Cube in episode 26, it boosts his usual portal power, teleporting the whole Giant Clock mecha to Mt. Zinit. The prequel episode "Noximilien" reveals that Nox had no particular talent for magic before he found the Eliacube. And as of season 2: Qilby merges with it to replace his missing arm and boost his powers...
All the cheerleaders (including Eva and Amalia) in the Bontarian Gobbowl arc wear bunny-eared headbands.
The Anime of the Game: A Western Animation example, though the Wakfu universe is technically cross-media. Subverted somewhat in that the game was originally supposed to be released in early 2009, before the series started, but it wasn't released until 2012). The game is also explicitly set a decade or so before the series. (Yugo's adoptive father Alibert is one of the few NPCs in the game, and Yugo is upstairs in his house as an infant.)
The Brâkmarian nobles. They were planning to use The Mmmmmmmmmporpg as a weapon against Bonta.
Remington's nemesis, Ush Galesh, who is, in addition to being one of wealthiest individuals in Bonta, is an insatiably sadistic murderer and just happens to be the son of Ecaflip, and therefore a demigod.
Artifact of Attraction / Artifact of Doom: The Eliacube. In "Noximilien", it induces unhealthy obsession in Igôle, then with Nox, leading to paranoia and delusions of grandeur. The loss of his family is more the last straw pushing him over the edge after a long descent than a real trigger for his madness. Whether the artifact can really talk to Nox or the Xelor is just hearing voices is left unclear, but the latter is more likely.
No wonder Yugo is extremely wary of using the Cube at the beginning of season 2, even in order to discover the fate of his people, fearing that he could become like Nox.
Qilby on the other hand, knows how to get the most mileage out of the Eliacube with no apparent detrimental effects. His particular brand of insanity wasn't caused by the Eliacube.
Can be seen in episode 14, when the tribe's old chief, Botan Ficus, tells his story. The flashback is in a primitive/tribal art form.
Also, a minor one in episode 12 ("Gobbowl Hell 3"), with an artist making a very stylized painting of the heroes.
During the brawl in episode 19, there's a few shots who clearly mimics the style of Street Fighter IV art.
The specials, like "Noximilien" or The Legend of Ogrest, are in a different art style than the main series.
Ascended Extra: Several minor characters get their own graphic novels in the WAKFU Heroes series: Kabrok & Miranda (Le Corbeau Noir), Percimol, Remington & Grany, Maskemane, Elaine & Encre Noire (Tangomango).
Asteroids Monster: Mocked during the season 1 Title Sequence, with Yugo jumping onto some sort of gelatinous cube monster who splits into many smaller, cutesy-looking cubes.
Badass Boast: Rushu and Goultard allow themselves duelling Badass Boasts:
Rushu: The gods are too weak for me to worry about them, you little worm! And it's the same for you: you're just a shadow of your former self! Goultard: Which is still more than enough to sent you back from where you're coming. With your slip as handkerchief to wipe out your own tears.
Battle in the Rain: The final battle in episode 26, with Adamaï and Yugo versus Nox, happens in the rain at Mt. Zinit. It is used to great visual effect when Nox stops time, and the raindrops first stop falling, hang in the air... and then rise upward when he reverses time.
Sadlygrove's sword is the prison for a demon. While it makes it a potent weapon, it can in turn possess him if he lets his guard down.
Qilby is practically the embodiment of this: As one of the original six Eliatropes and their dragon siblings, Qilby is immortal. Unlike the other five, Qilby remembers all his past lives. This might seem pretty useful, and probably was for a while, but after thousands of years, being unable to forget has driven him well and truly insane.
A Bloody Mess: In episode 13, to fit with the overall horror-spoof theme, Sadlygrove spreads red berry juice everywhere.
Body-Count Competition: Sadlygrove and Rubilax have an impromptu one in season 2 episode 9. Problem is, Sadlygrove can't count.
Bond Villain Stupidity: Rushu. Wanting to play games with the heroes gives them a chance to escape, although Remington and Grany don't quite make it.
Boobs of Steel: General Frida Mofette by a long shot. Her gender is obvious from a top view, and she's a Blood Knight bordering on Ax-Crazy when you put her in a mech. Heck she considers a war a vacation.
Boomerang Comeback: Attempted by Yugo with his wakfu shield in season 2 episode 25, but Qilby manages to parry it on the return.
Oh Crâ, episode 19. Sadlygrove, possessed by Rubilax, proceeds to crush both forearm and bow of Love Interest Evangelyne in one grasp. The tears of physical and emotional pain she show afterwards are enough to cause a My God, What Have I Done? moment in Sadlygrove, who is arguably also made a broken cutie.
And again in episode 25. Eva just can't catch a break.
She was this close to being even more broken when Amalia became a tree. It was averted that time, thank Crâ, but poor Eva seems like a Cosmic Plaything...
Bring It: Sadlygrove to the Sadida warriors in episode 19.
Broken Pedestal: Yugo is initially in awe of the Justice Knights, but once he finds out how callous and hypocritical they are, and that even career criminals like Remington Smisse are capable of noble acts, he isn't quite as taken with them as he once was.
Bubble Pipe: Shanon Stone owns one with a cigarette-holder look.
Several Call Backs in season 2 episodes 2-3 to season 1 episode 6, with the return of Vampyro's castle and his ghouls.
Season 1 episode 9: "I don't like clicks..." Season 2 episode 5: "I really don't like clicks..."
Season 2 episode 18: "Another of that thing? We're gonna end up in our undies again."
Calvinball: Gobbowl. It seems pretty straightforward at first... but rules get thrown out the window about halfway through. In Bonta, a totem pole rises out of the ground and inflicts some effect chosen by the audience on the field, just for fun. And in Gobbowl, cheating is part of the sport.
The Cameo: Tons and tons. We can split them up in to types:
Internal cameos, which show characters from previous (or future) episodes out of context.
For example, you can see two of the princesses from episode 4 in the crowd in episode 10.
Goultard's mother is in the background in episode 3, heaving a heavy basket exactly like her initial appearance in a previous Ankama short film.
Ogrest, the monster that started the troubled age of Wakfu all by himself, makes a brief appearance in episode 26. You'd have to know the universe's backstory to understand what he's doing there, or even who he is, since it's not explained in the episode.
External cameos, which display some of the author's tastes in anime and series. Frequently in the background or in a crowd.
Camp Gay: Canar and Renate don't even try to be subtle about it. Renate himself is named after the fabulous Renato from the film/musical La Cage aux folles.
Can't Live Without You: The Tree of Life holds the lifeforce of the whole Sadida people. Which means that when it is drained of all wakfu in episode 26, everyone of them turn into inert stumps, including Amalia.
Cerebus Syndrome: The show starts off as very fun and colourful, and even the tragic Break the Cutie moment in episode 19 is created by somewhat silly circumstances (namely Sadlygrove insulting Armand's halitosis, and Armand spanking him repeatedly with a vine whip). But once you hit episode 24, Ankama takes all of your silly expectations of an innocent Saturday-morning kid's cartoon and utterly shatters them by delivering the darkest, most tense, and most heart-breaking season finale French animation has ever seen.
Chained by Fashion: Anathar, after escaping from the Justice Knight's prison, keeps the enormous manacles and chains around his huge wrists.
Remington does this to Evangelyne in season 2 episode 2.
Also happens to Amalia in episode 24 of season 2.
Cliffhanger: An infamous one at the end of episode 15, which acted as a mid-season break while Ankama and France 3 worked on finishing future episodes and scheduling. Not knowing what would happen to the heroes who were caught in dragon's breath, and knowing that the answer was only going to come six or seven months later was quite annoying.
Clock Punk: Not applicable to the whole setting, but frequent examples show up.
A continuation of the cartoon following Season 2; fittingly in a format typical for Manga.
Also the WAKFU Heroes series of graphic novels featuring minor characters from the show: Le Corbeau Noir (Kabrok & Miranda), Percimol (the Dripple hero), Remington Arc 1 and 2 (Remington & Grany), Maskemane and Tangomango (Elaine & Encre Noire).
Companion Cube: The Eliacube, which is regarded as sentient by Nox. Whether it really is or not has been left unclear.
Continuity Cameo: Despite being placed a thousand years later, the series continuously makes references to the original Dofus game and universe.
The most obvious example would be the animated trees in episode 2: the episode references a story from one of the Dofus comics, Le Chêne Mou.
Goultard, a major character of the Dofus comic, makes an appearance in episode 22 and at the end of season 2.
Ogrest, an important background character of the Wakfu game, makes a brief appearance in episode 26.
Wakfu is also big on cross-media. Most places from the series can be found in the Spin-Off MMORPG, The Guardians.
Convection Schmonvection: Brâkmar is built on volcanic ground, with lava rivers flowing below several parts of the town, which should make the whole city too hot to be liveable. The Gobbowl Stadium itself is above a lava lake.
Creative Closing Credits: The credits of each episode have a small scene acted out by a character or characters from that episode alongside them. The first four episodes are simply the main characters introducing themselves, but the following episodes all have little skits attached.
Creepy Souvenir: Qilby's collection of various animals from all the planets the Eliatropes harvested.
Cruel Mercy: Amalia does this to Ruel in the first episode of Season 2. After realizing it was him that was causing all of the critters from underground to terrorize the Sadida people in his search for gold, she decides to not throw him in jail in exchange for all of the gold he found since it rightfully belongs to the Sadida people. Ruel pleads to have his head cut off instead, but she doesn't listen.