To be fair, Nintendo's doing a lot of things lately that people said they "really don't see them doing". Some good, some bad.
Like I never thought I'd see DK in a biker suit and Bowser clad in armour in Skylanders, but here we are.
If we want to bring up Wii U crossover material, there's also Sonic dressing up in Link cosplay and Bayonetta dressing up as quite a few different Nintendo characters. Of course, Sega has a bit better of a relationship with Nintendo and was being paid for those games to be on the Wii U, but it's still interesting.
Then for the 3DS there's the Nintendo costumes in Monster Hunter mixed in with all the other crossover costumes. And Chrom, Lucina, and Fiora in Project X Zone 2, which was already an insane crossover game between three companies to begin with.
None of it's quite as notable as Nintendo characters with odd redesigns in a Western game, but Nintendo crossovers have been happening a lot more frequently than they seem to have in past generations. Might be to a degree Sega wanting a bit more exposure as well since their hand in one way or another is in every pie listed here, but they weren't exactly the only party involved in half of this either.
Honestly I hope it keeps up at this pace if not somehow becomes even more frequent. Crossover material is pretty fun, and even at it's oddest stuff like this is a bigger win than things like car and gas station commercials in Nintendo's own games.
. . .OH, I remember another Western crossover that was unpredictable. That Mario skin pack for Minecraft. That's less work for the devs than the Skylanders, but it's also a bit out there considering Minecraft alone is a bit of an oddity on Nintendo systems due to who bought it out. And AFAIK that's the first crossover material coming to the Switch, too.