On Friday, November 4, 2022 at 10:53 PM EST, a player with the name "PC" joined the skyblock server. As we know that 2 letter usernames are illegal and somehow the person was able to have a 2 letter username https://imgur.com/a/Pfjoccs
Image 1:
Photo of the player named "PC" joining Skyblock
Image 2:
Proof that 2 player names are illegal
EDIT: According to Ria, the account might have been made in 2010 before the limit was in place.