If you were to write a Ninjago crossover, what roles would you put the Ninja and co. in? Would you replace other characters with them, or just put roles from the franchise? Anyway...

Splatoon (I've been playing that game a lot, it's pretty fun):

Jay: Octoling (his signature animal is an octopus) (or maybe an anemone, since they shock you and he has such untamed hair) (yes, there are anemone people in this game) (plus he's adopted, so being a different species might make some sense)
Nya: Inkling or betta fish
Kai: Inkling or betta fish (since he's related to Nya; otherwise he'd be a sea urchin or something)
Wu: Whatever the heck Cap'n Cuttlefish is (they say he's just a very old Inkling, but I'm not really sure)
Lloyd: Inkling-Octoling hybrid (since he's a hybrid in canon)
Garmadon: Octarian (maybe Octoling in his temporary "good" form)
Cole: "Sanitized" Octoling, maybe, considering his past (both his fathers' expectations and his time as a ghost), or maybe a formerly "sanitized" Octoling who got cured (also, Octopi are strong, so that could be part of why I chose that)
Zane: Robo...ling....? I'm not sure.
Dareth: Maybe a jellyfish? Some side-characters in Splatoon are jellyfish.
The majority of villainous species (skeletons, Serpentine, etc.) would probably be Octarians as well.

Harry Potter:
Jay: Hufflepuff or Ravenclaw, major in Flying and Astronomy (if there's a Magical Engineering class, that would probably be his best subject) (he might also be a Quidditch player)
Kai: Gryffindor or Slytherin, major in Defense Against the Dark Arts, possible Quidditch player
Nya: Gryffindor or Ravenclaw, major in Herbology and Charms, possible Quidditch player
Zane: Ravenclaw or Hufflepuff, major in Arith...well, pretty much everything, but Arithmancy, History of Magic and other logical subjects are his favorites
Lloyd: Gryffindor or Slytherin, majors in DADA
Cole: Hufflepuff or Gryffindor, major in Care of Magical Creatures
Wu: Headmaster or professor