how the hell is a mini with wide arches and buckets a sleeper.. it looks awesome
A sierra saph with a rollcage I would question a little as well
likewise a MR2 would not shock me if it was quick as its a supposed to be a sports car

A sleeper is supposed to catch you sleeping with its performance.. not yell about it imho

My car is more of a sleeper than some of the things posted in this thread, yet I would never consider it a sleeper myself