When representing Kirby, I really hope they don't use enemies such as Marx, Zero, Magolor, or Sectonia. I don't think a world that is presented as fun a cuddly should be shown as dark and gritty. I feel that bosses such as Kracko, Dyna Blade, and Whispy Woods fit in best.
So, here's how I'd like it:
Smash Run Boss - Dyna Blade:
Dyna Blade, originating in Kirby Super Star, was one of my favorite bosses from that game. Being in one of my most favorite sub-games from Super Star, I'd love for her return. If she was included in Smash Run, she'd appear more than often at the top of the map, and then land down. She'd behave similarly to how she does in the game, landing on the ground and using several attacks. This includes spitting hot air pockets at the player, grabbing the player and strangling them with her talons, finishing it off by throwing them away, flying up and then swooping through the background (similar to Master Hand), or trying to peck at you. Dyna Blade would have her weak spot on her head, while hitting anywhere else would do less damage. After being defeated, she would screech and fly out the screen, leaving behind several power-ups for the players to use. We already have Bonkers as a Smash Run boss, however, so it may be a bit unlikely.
Stage Boss (3DS) - Kracko:
Kracko has appeared in all of the platforming Kirby games except for Kirby 64: The Crystal Shards, and Kirby's Return to Dreamland, making it a staple boss character, similar to Whispy Woods. Kracko could reside in a new stage, Bubbly Clouds, which could appear on the 3DS version. This is due to the fact that Kracko has appeared in Kirby Triple Deluxe, which means that adding it into the game would be fairly simple. Kracko has several attacks, making it out to be a very unique and detailed boss, which can be seen
here. Kracko would take its Kirby: Triple Deluxe first stage attacks (before it reaches half health), which are its classic moves. When spawning in, Kracko Jr. could appear in the background before flying in and forming into Kracko. When defeated, it would have the same animation he has when he is defeated (basically de-forming itself), obviously. While fighting, he could occasionally spawn in a Waddle Doo, which would work out fine as King Dedede can't throw them anymore. Kracko has also appeared as a stage hazard in Kirby Fighters, which was also in a Bubbly Clouds stage. He would be very easy to implement into the 3DS version, as both the stage and Kracko itself can have all their assets taken from Kirby: Triple Deluxe, hence being a 3DS exclusive stage and boss. Also, for music, as 3DS stages use two tracks, he could use K:TD's Boss Theme as one, and use the K:TD version of
Bubbly Clouds.
Stage Boss (Wii U) - Whispy Woods:
Whispy Woods has been the staple boss of the Kirby franchise, appearing in almost every game to date. Whispy Woods has also appeared in a stage alongside every single Smash Bros. game, which is Dream Land in Super Smash Bros. and Green Greens in Melee and Brawl. He would appear in a new Kirby stage, whether it be Cookie Country, Green Greens, or Dream Land. I feel as Cookie Country would be the biggest contender, as it would be the perfect stage to be revealed alongside Bandana Dee. Whispy Woods would be present in the stage at all times, being a "permanent boss". He would be in an idle mode most of the match, then get angry after a while and shake his leaves. This will trigger his active mode, in which he will start attacking. As Whispy is an easy boss, this should be expressed in the games too, with him being an easy boss with weak attacks. He would drop apples, spit air puffs, and occasionally inhale a player as shown in Return to Dream Land. He would be finished fairly fast, in which he would go into a defeated state for the rest of the match, such as in Kirby Air Ride. If he is not defeated before he stops attacking, he will recover his health and go into his idle stance once again. Music for the stage could include
Return to Dream Land's theme,
Green Greens (remix from Smash Direct),
Cookie Country,
Gourmet Race, and more.
Reposting both of these due to detractors:
I would like to remind everybody that we already have Knuckle Joe (and now Nightmare) as assist trophies, and I'm highly doubting that Bandana Dee would turn into an assist instead of much more fit characters, such as Adeleine, Gooey, or Dream Land 2 and 3's Animal Friends. I would think that Adeleine would be the most fit for a third Kirby assist trophy, as she could paint items such as Maxim Tomatoes and throw them out to help the fighters, or she could use some of Ice Cream Island's Boss, Paint Roller's attacks. This includes Waddle Dee's, Nimbus, Cars, Baseballs, Parasols, Bombs, Microphone, or even Kirby. These would all work out correctly as painted enemies to be thrown out and wouldn't be confused with other things due to the fact that they're all crude paintings. The other biggest contender for Kirby's second assist trophy would be his Animal Friends. This assist trophy could use Triple Deluxe's assets from Kirby Fighters stage, Coo's Forest. The assist trophy could randomly select Rick, Coo, or Kine that can come through and attack opposing players.