Fell off a Truck
Was stolen, lifted, burgled, etc.
"Where did you get that expensive new V.C.R. and Bicycle?"
"They fell off a truck."
"They fell off a truck."
Fell off the truck
Stolen; Something obtained or being sold illegally.
"Hey dude, Check out this new PS3. Only paid 50 bucks for it because it fell off the truck."
"You lucked out, man."
"You lucked out, man."
fell off the turnip truck
Dumb. Stupid. Implying that you've been isolated from the world (on a turnip farm).
He understands what you're saying. It's not as though he just fell off the turnip truck.
just fell off the turnip truck
Naive. Implies rural unsohistication versus urban savviness.
"A Rolex for $50? Do you think I just fell off the turnip truck?"