Slightly reminded of the story about the guy who went into his local VW dealer and asked to test-drive a Golf GTI (which he could afford to buy). They did whatever (formal or informal) checks they normally do, and gave him the keys.

He drove it across town to the BMW dealer, and told them that his new GTI wasn't fast enough for him and he was interested in trading it in for an M3.

Repeat at higher- and higher-end car dealers until he's in a Lamborghini by lunchtime, which he then had a few hours to drive around in before he went back returning all of the cars...

[Of course, this only works in countries which don't have special easily-recognizable license plates for cars owned by a dealer.]