I’ve discovered something curious.
Maybe you’ll remember that a few years ago there was another leak, and we got to see some flash assets. I’ve been going though them today and I found out that Derpy was originally named IPG07 (ie, Incidental Pegasus 07). This isn’t new information, many ponies have unspecific names, even some of the ponies who appear in the group shot of the new intro (the ice cream cutie is SOF_F02, School of Friendship - Female 02, I assume).
Derpy is a character now, and her name in the most recent assets is DERP. The interesting thing is, IPG07 is still there, they just changed the colors and the cutie mark to use her as a background pony. DERP is a slightly different new character, and her colors aren’t even the same from the ones of her original puppet.
Top: old and new IPG07, bottom: DERP.