In episode 6, Spirit of the Ducks, Ken Wu is there as the 6th member of the old Ducks. However, Ken was never a part of the District-5 Ducks. He was only on team USA Ducks. Same thing with the last episode when the old jerseys are given to the Don't Bothers. Russ Tyler, Ken Wu, and Julie Gaffney jerseys are seen when none of them were part of the original District-5 Ducks.
The Original Ducks numbers were given to the new Ducks in season 2, which is against the rules. Retired numbers cannot be used by another player of the same team once they have been retired.
Throughout the series the players do not wear mouth guards. USA Hockey, the governing body of youth hockey in the United States, rule 304 (f) requires all youth players to wear "internal mouthpiece that covers all the remaining teeth of one jaw, customarily the upper."