Coming from the "Why?" files of bike parts: Quick Release Pedals.
These bad boys are about $50 and available here.
Quick release pedal
Why would you want these? Best I can tell, if you want to deter thieves or have your bike narrower for a bus or train ride or storage. I guess they work like air hose fittings. Except when they fail, instead of air leaks you get horrible bicycle crashes ending in sterility.