Seven card Stud Poker. If throughout the course of cards being dealt face-up, a Two appears, then all Twos are wild in all hands. If this is established, and later a Three appears, then all Threes are wild in all hands (with Twos no longer wild).
These cards have to appear in sequence, and this wild-card reversal continues to Fours and up, should they be dealt face-up in the game. If a Two does not appear throughout the course of the game, then there is nothing wild, and it is played as regular seven card stud.