For Ultimate Cheese: You need a bare minimum of 8-16 races on Rock n Roll racing, two levels of Lost Vikings, half a level of Blackthorne and the Final Boss no hit.
blizzard is a small indie multi dollar company, you gotta cut them some slack. Heavy usage of save stating for Blackborne's perfect hit trophy is recommended, my hat's off to anyone who does that legit.
Ancient Ruin Depths Floor 8: Once you kill Robztep, he unlocks a once a day Boss Rush that has ALL of the Bosses in the game in a row, and they can all be stolen from. Got my Platinum a short while ago. You do NOT need two playthroughs to Plat.