What are the keyholes to appear in Kingdom Hearts 2

The different keyholes are after you visit the first time and you get an object after the last boss you visit 2 times in each world like Atlantica is a bubble and when mielificent sucks you in to a dark place it is a salty sea ice cream bar from xeknort/riku he chose that form as ansem in Kingdom hearts 1 he actually was xeknort ansem the wise's assistant riku chose that form and king mickey promised not to tell sora:)