The Happening Space, also known as the Green Space or ? Space, appears as a space in the Mario Party series and appears in all boards. The happening spaces are depicted as a green space with a question mark as the space symbol. When a character lands on a happening space, a specific event occurs which depends on the board map that the character is playing on. The events have a wide variety effects that may affect the characters' positions, their coin and star amount, and their number of items. The events may also affect certain aspects on the board like creating new obstacles or introducing new characters to the board. In Super Mario Party, happening spaces are referred to as Event Spaces and now have an exclamation mark icon.
Happening spaces have made an appearance in every Mario Party game and on every board map. Their effects may differ depending on which board map is being played. These effects are usually based on the physical attributes of the board. For example, in Mario Party 2, if a Happening Space in Western Land is landed on, then it will make the train go on to the next station, which may hit players in its way and send them back to start.
After the end of a game in most Mario Party games, a Happening Star is awarded to the player who landed on Happening Spaces the most, assuming the Bonus Stars option was on during the game. In Mario Party 7, several new options for what could be the Bonus Stars are added and Happening Star is not always to be selected as one of the three given to the players.
In Mario Party 3's Duel Mode board, a special Happening Space appears that simply gives a three-item roulette that features many events such as recovering all of their health, stealing the opponent's spaces, switching the partner locations, gaining coins, and several other outcomes.