I've seen some fast subcompact sleepers. Take the Micro Image's 12-second Yaris, for example. My Yaris, with intake, header, and exhaust is probably a high 16-second car at best. The Yaris above, although not exactly "sleepy" looking, likely surprises most people. Love it.
Or how about a 12.53 second Ford Festiva (no not Fiesta, Festiva) with a rear-mounted turbo. Yes, that would be a heck of a sleeper. Who the hell would expect that? Not me. Bonus points for the front wheel treatment.
Or how 'bout this: A V-8 shoehorned into a Suzuki Sidekick. Hmm ... who do I know that already has a Sidekick? (ME!). No one would expect that. Although, I'd likely opt for a 2WD version and keep the Teal Terror for my off-road toy (that 1.6-liter motor would feel mighty underpowered after driving one with a V-8).
So who's with me?