I wouldn't say that inclusion in Smash Run counts as "a big deal." Then you could say the same thing about Chandelure or Roturret.
Chandelure is one Pokémon among hundreds that the developers thought would work as well as any other and served as an advertisement for the latest Pokémon games. The Kremlings are a specific group of enemies that haven't appeared in years, and haven't had any
notable appearances in even longer. Both Chandelure and the Tiki Tak Tribe are from recent games and are included as advertisements for those games. The Kremlings are nothing more than the
former enemies of Donkey Kong, and have more or less been forgotten by their actual creators. And yet Sakurai still thought they were important enough to Donkey Kong's history to warrant being enemies, even over the Snowmads, the enemies from the latest game.
Yes, this is a big ****ing deal.
Wow looking at this, K.Rool never appeared in a first party developed game aside from his trophies in Smash.
I never realized it, but that's interesting.
Smash is developed by HAL, actually, so it's no more a first party game than the actual DKC games were, really.