Thought I'd try another, so here's Oshawott and Dewott.
Oshawott: "Sea Swordsmanship (Beginner)"
(two themes to this: lesser experienced sword users, and water stages that are very prominent at first but then gets rarer and less of use until the end)
Stage 1:
on
(
The Great Sea)
[references the starts of Wind Waker and Phantom Hourglass]
Stage 2:
on Great Bay (
Ocarina of Time Medley)
[Ocarina of Time young Link was less experienced with the sword at his start]
Stage 3:
(default look) on Wuhu Island, specifically the target-shaped arena (
Wii Sports Resorts remix)
[References the event in Wii Sports where after losing a round, the Mii is still soaked from having been recovered from water]
Stage 4:
(x3) on Pokemon Stadium, specifically the water transition,
(x2) as allies (
Red/Blue Medley)
[referencing triple battles from Pokemon Black/White, also last water-themed stage before the last regular stage]
Stage 5:
(default) on
(
Crimean Army Sortie)
[referencing the start of Path of Radiance, only dry stage in the entire route]
Stage 6:
on Kalos Pokemon League's water chamber (
N's Castle)
[referencing Pokemon XY and its easy difficulty curve especially for a Pokemon imported from a previous title as those get extra experience points, contrasting with the game's native starter being made to evolve earlier]
Boss:
Giga Bowser (
Battle! Reshiram/Zekrom)
[slight injoke at March 10th being affiliated with both Oshawott
and Mario]
Dewott: "Sea Swordsmanship (Advanced)"
(same as Oshawott but more veteran swordsmen instead as well as less water stages meaning less terrain advantage. Kinda seems more like a continuation even)
Stage 1:
on Fountain of Dreams (
Meta Knight's Revenge)
[sets the theme for future matches, also a Kirby's Adventure second-to-last boss reference]
Stage 2:
(knight armor, default everything else, x2 but the second one is red instead of blue) on Find Mii (
Find Mii / Find Mii II Medley)
[references the summoned StreetPass heroes in Find Mii, also changing to a dry stage much earlier in the route)
Stage 3:
(Radiant Dawn alt),
(Black Knight full costume) on
throne room (
Against the Dark Knight) [Free-For-All]
[clear reference to the Black Knight fight from Radiant Dawn]
Stage 4:
on
(
Battle! (Trainer Battle) - Pokémon X and Y)
[references Super Training and online battles from X/Y)
Stage 5:
(Tunic of the Wild),
on Hyrule Castle omega (
Death Mountain)
[references the SpaceWorld demo of 2000, and to a lesser extent the Hyrule Castle in Breath of the Wild, only visible water in the area is far away so no terrain advantage]
Stage 6:
(
after two KOs) on Midgar (
Lords - Showdown but switches to
Fight On! when Cloud comes in) [Free-For-All]
[References Fates's amiibo functionality and Awakening's Outrealm fighters in the first half, and Cloud's super soldier status in both second half and stage, the latter also having water only as vapour]
Boss:
Ganon [
Battle! Reshiram/Zekrom]
[Ganon also uses dual swords, contrasts with Oshawott fighting Giga Bowser since Ganon's a boss in the dark map while Giga Bowser is on the light map. Stage is on fire also, which means terrain advantage is null]