Explanation
This is a memory trick for which way to turn your front wheels when parking on a hill, borrowing Superman's catchphrase "Up, up, and away!" for the uphill case. When you're parking UPhill next to a curb, turn your wheels AWAY from the curb: if the car's brakes ever fail, it will roll back only a few inches before a tire catches the curb, instead of rolling into traffic.
When you're parking DOWNhill, do the opposite and turn your wheels TOWARD the curb, so a runaway car rolls into the curb instead of into the street. If there's no curb at all (just a shoulder), turn your wheels toward the edge of the road either way, so the car rolls off the road rather than into oncoming traffic.