A bug in poker is a limited form of wild card. One or both jokers are often added to the deck and played as bugs.

The bug is played as an ace unless is can be used as missing card to complete a straight or flush. For example, the hand K-K-X-5-2 is just a pair of kings (with an ace kicker), but any four same-suit cards with a bug make a flush, and a hand such as 7-X-5-4-3 makes a straight.

In draw poker, when a bug is in play, this makes the highest possible hand fives aces, rather than a royal flush, and also increases the odds of improving a hand when drawing to three of a kind with an ace kicker.