Grab bag

What's the acoustic equivalent of a mental image? Mental music? I'm thinking of starting a collection of ones that amuse me, and so far I have the following:

• Luciano Pavarotti singing "In the middle" by Jimmy Eat World
  
• Big band jazz rendition of the Super Mario Brothers 2 theme song

In other news, my sandwich bread got moldy (and it's only Midweek! according to German). So I improvised and threw together a salad with spring greens, shredded sandwich meat, blueberries, and croutons crumbled from thomasyan's nigh-indestructible toast. It is very tasty.

Yesterday the shuttle to work was having trouble going up a sloped driveway, and could not make it even after all of us passengers disembarked. The driver ended up solving this problem by reversing direction and backing up the slope, which the bus did with remarkable ease. So how does it work that the bus cannot go up the slope forwards, but can do so perfectly fine backwards?