I believe that Jokers (one) is used in some poker games and when used it commonly substitutes for an ace and can be used to complete a straight or a flush. I do not know if a Joker ace is subordinate to a natural ace. If not, then the possibility of a tie full-house exists, i.e., A-A-Joker-x-x vs. A-A-A-x-x, where "x" is the same four cards.

Jim