If you win a game of blackjack can someone put down a joker and bring you back?

In blackjack, a joker is not typically used, as the game is played with a standard deck of cards, usually without wild cards. Winning a hand means you have a higher total than the dealer without exceeding 21. Once a hand is finished, it cannot be altered by introducing additional cards like a joker. Therefore, if you win, there is no way for someone to bring you back into the game using a joker.