In Canasta it is possible to pick up the discard pile, and it is often advantageous to do so since the more cards you have in your hand, the more options for making canastas and melds there will be. The only way that you can pick up the discard pile is if a player has a natural card in their hand. A player is only allowed to take the discard pile at the beginning of their turn. To take the discard pile, the player must show the pair that matches the top card and meld those cards immediately. The player then takes the next 4 cards in the discard pile, for a total of 5 cards.
When a player discards a wild card, the discard becomes frozen and remains frozen for the rest of the round. Unlike Classic Canasta, this is the only way the discard pile is frozen.