I've learned that buying a bulk of one minion is better than buying a single of another (unless it's dragons, because dragons are immortal in the game)
Nyan Cat comes from a nuke that cost $1,000,000, but you have to nuke a coin box from Germany while being really good with an experimental machine gun. Follows those rules exactly and you should be good. Oh, and don't forget the overalls yodeler hat, the three man band, and the conveniently placed shop that sell these weapons and the nuke.