When three-letter airport codes became standard in the mid-1930s, airports that had been using a two-letter identifier simply added an X to their code, which is why Los Angeles International Airport is known as LAX.
While it's up to individual states to determine the color of school buses, most have been painted National School Bus Chrome Yellow since a 1939 national conference recommended it as the shade of choice.
DID YOU KNOW? Marlon Brando hated memorizing lines so much that he posted cue cards everywhere to help him get through scenes.
He even asked for lines to be written on an actress's posterior. (That request was denied.)