Past Nissan Cube owner here reporting that you can stuff a twin mattress against the ceiling of the car, supported by the heads of the driver and passenger, for several blocks.

I did the same with a Smart. The pickup functionality of the back door also allows for moving a fridge, if you tie it down appropriately.

I moved a queen bed frame and mattress in a 2006 mini convertible.

You should see the way I use my Cayman. It’s starting to see more track miles than road miles. Finally using all the speedometer I paid for.

Pah!

I fit 9 bales of hay in a Saturn Vue. I'm still really proud of that :-)

What kind of bale of hay? Where I live, a bale of hay weighs something like 200kg, total weight would be 1800kg which I don't think any car could muster (nor actually fit), but seems you're using "bale of hay" as a different measurement than what I have in mind.