Red Card! is the name of Diddy Kong's Super Ability in the game Mario Strikers Charged. It can only be used when Diddy Kong uses his Special Item, which is depicted as his own head. Once Diddy has used this item, he will summon a beam of light in front of him, which will cause any players who walk into it (opposing team or not) to be sucked into the air. They will disappear for at least 15 seconds. This is a very useful Super Ability, and if all the opposing players are caught in it (which is very rare), Diddy Kong is free to perform a Mega Strike without any disruptions.
Red Card!'s name comes from the penalty card commonly used in football. Any player who receives a red card is ejected from the game and forces their team to play a player short (actual term is "Send Off"). Players can receive red cards due to a major infraction of the laws of the game, or if the player receives a second yellow card. If a team gets 5 red cards, they forfeit the game, as they need 7 players to play. This is in line with the Super Ability's effect.