Galactic Civilizations II again, because only this game lets you create a civilization of people with less than average intelligence, then use cultural influence to subvert other cultures and gain prevalence. Btw, this is technically on-topic, as the topic says "What game did you last play".
I had a really funny weird glitch in the Deep Dark Galaxy Purple Coin mission I spun a Boo and it moved into a Toad and dissapered and left a Coin. It was owned by Toad!