Well, the one other thing I would like to talk about mini-bosses are the thought, effort, heart, and, oftentimes, soul in giving mini-bosses their unique, original designs... along with making them not too repetitive in their appearances.
The Mega Man and Kirby series do have many games that feature mini-bosses, though their amounts and originality really differs.
Many Mega Man games have mini-bosses, but only in select stages, not in each. The one thing is some are fought more than once mid-way through select stages, even with hazards place in to make these battles a bit tougher, like Paozo from Mega Man 9, fought not once, not twice, but THRICE in Concrete Man's stage, all in a row. Granted, that game was made for WiiWare, as well as PSN, and XBLA, and that's fine by me, but still.
Being that many were made for NES, SNES, and PS1(despite the CD's storage size that could've guaranteed some more, then), it seemed like there weren't much, due to the former's carts holding little space for game content at the time, even on SNES because the sounds are comprised of recorded DPCM samples, at least until Mega Man Zero, ZX, and ZX Advent, had a bit plenty more in these games.
Mega Man 11 was first game in the whole series to have a mini-boss fought in each of its main stages, and that gave me some satisfaction in fighting them in their own chosen stages. I fought them, and it was more fun.
Kirby's Dream Land, the first Kirby game, debuted mini-bosses, Poppy Bros. Sr., Lololo, and Kracko Jr., all original, and Kirby's Adventure introduced many new mini-bosses that went on to become recurring in many games to come, such as Bonkers, Mr. Frosty, Grand Wheelie, and Bugzzy.
What I don't find it select games in that series trying to make any regular enemy a mid-boss, like Waddle Dee, for instance. Sure, it may seem like any one enemy's trying to prove capable of being one, but it doesn't do any good being original, nor uniquely creative.
We had more new mini-bosses in later games, but others weren't chosen to reappear, like Batafire, Bombar, Gao Gao, Miasmoros, Water Galboros, Super Bonkers, Box Boxer, Big Metalun, Tedhaun, Rolling Turtle, Boxy, and Phan Phan. King Doo, Blocky, Gigant Blade, and Kibble Blade did reappear, but I feel they're more better favorites chosen for their reappearances as somewhat of a priority than having new mini-bosses to fight.
Kirby: Mass Attack does have mini-bosses, mostly unique, others slightly.
Super Kirby Clash have different variants of select mini-bosses and regular bosses, being mostly about battles and such, being a spin-off; Kibble Blade was given, Frost Kibble Blade, Bonkers was given Spark Bonkers, Kracko was given Venom Kracko, and Gigant Edge was given Gigant Edge was given Ignite Edge, and Ice Dragon was given Electric Dragon. all neat variants with designs that stood them apart.
Here's image links about their concept art...
Venom Kracko and Frost Kibble Blade -
https://cdn.wikirby.com/b/b7/SKC_Venom_Kracko_and_Frost_Kibble_Blade_concept_artwork.jpgIgnite Edge, Spark Bonkers, and Electric Dragon -
https://cdn.wikirby.com/7/72/SKC_Team_Elementrio_concept_artwork.jpgWhat I find quite disappointing from Kirby: Star Allies, and Kirby and the Forgotten Land is that they only have one new, debut mini-boss, whereas all the rest are just recurring mini-bosses from past games, the latter given "Wild" re-appearances. I can easily recognize their designs.
I'm feeling in my mind sometimes the designers behind Kirby are kinda having their own creative blocks in trying to create new minibosses in new games. Its a bit worrisome because it takes away brevity, and it doesn't add much to the series' overall bestiary total.
Zelda's Tri-Force Heroes' worlds in The Drablands all have mini-bosses fought at the end of their second dungeons, being stronger variants/alternatives of past and recent monsters, such as Electric Blob King from Buzz Blob Cave, Electric Blob Queen at Abyss of Agony, Freezlord at Snowball Ravine, Grim Repoe at Palace Noir, and Gigaleon at Deception Castle.
The reason they were not fought again in later dungeons is because they were given their own designs to stand out from normal monsters, and it keeps the game's brevity and ensures no single mini-boss gets fought more than one time. I find it enjoyable to fight unique mini-bosses without having to face them too many times or as downgraded enemies.
SMALL FACT: All the bosses, even the mini-bosses, were all designed by Grezzo's designer, Mikiharu Oiwa. That was confirmed true by that designer's answer via a post in Miiverse, while it was up.
I don't know if its more tougher to create new mini-bosses than normal bosses in new games, despite the more available RAM memory and stronger CPUs guaranteeing lot more than just bigger 2D levels and more mini-bosses to place them in, which I really like, but I think it shouldn't be. We have loads of tools, programs, and inspiration sources to create them. The matter is utilizing and harnessing them.
I felt like speaking more about them because their attention should be given more.