I've always found it interesting that the 6502 was little endian given that members of the team that designed it worked on the 6800 before, and that was big-endian. I keep meaning to comb through Chuck Peddle / Bill Mensch interviews to see if they comment on what led them to go little endian on the 6502.
"I used to be a big-endian fan until I finally figured out why the 6502 designers switched to little-endian: it let them start the addition of an index to an address on the LSB before the MSB was read, whereas if you read the MSB first you need to wait for the LSB addition before you know if you need to add a carry to it."
Also re: Mac OS Classic on little-endian... the only attempt I think was the "Star Trek" project, an attempt to build a Mac OS that ran on Intel hardware as a competitor to Windows: https://en.wikipedia.org/wiki/Star_Trek_project
EDIT, found it in this forum post on 6502.org http://forum.6502.org/viewtopic.php?f=1&t=6369&start=0
"I used to be a big-endian fan until I finally figured out why the 6502 designers switched to little-endian: it let them start the addition of an index to an address on the LSB before the MSB was read, whereas if you read the MSB first you need to wait for the LSB addition before you know if you need to add a carry to it."