I believe there are 19
Kirby Super Star featured a boss that would be battled in a RPG fashion reminiscent of Final Fantasy. Three bosses are fought together and are known as Computer Virus. While fighting them the hit points are displayed in a window in the background much like Final Fantasy.
Defeat All 10 Bosses Its Simple Really the easiest way is to be hammer Kirby or rock Kirby
Pretty much all of the bosses. (correct me if I am wrong) Bowser could be FIGHTING the final boss, too. (ex. Mario and Luigi, Bowser's Inside Story, etc.)
I assume you mean control with the Ghost ability. You cannot control Bosses or Mini-bosses with Ghost. Only regular enemies.
Yes it's a lot harder with less HP and stronger bosses
The levels are a lot harder because Kirby only has half health and the bosses are a lot more difficult to beat.
you have to beat at least 13 bosses in The Arena
The Ozma and Tantarian.
your mom and you
The best Pikmin for beating bosses including the Burrowing Snargret and the final boss is a team of 100 Rock Pikmin.
Hero = 8 bosses, Dark = 8 bosses, Last = 2 bosses so 18 bosses in total.
I don't know any action replay codes, but you can turn into Super Sonic (and Burning Blaze) in Sonic and Blaze mode. You unlock it after beating the final-final bosses. You unlock the final-final bosses after you get all the emeralds.