Bowser Time is a new kind of event in Mario Party 7. This event happens every five turns, and this only appears on Party Cruise mode. After every turn, a gauge shaped like Bowser's face fills up; when it's completely full, Bowser comes and creates chaos for the players. There are many things Bowser can do, depending on the board.
Bowser will take a photograph of the players, then make them pay 10 or 20 coins for it. Sometimes, he'll "stumble into" the photo, but this has no effect on the cost at all. After making everyone pay their coins, Bowser will leave without giving anyone the picture, which Toadsworth points out.
Bowser will crush one of the Orb Shops and make it his own, entitled "Bowser City". The first person to pass by Bowser's shop will be forced into buying a useless item for 20 coins, which could either be a Golden Bowser Statue or a Koopa Kid Orb. After paying for the item, Koopa Kid will come and steal it from them, and the shop will disappear. If a player passes by without any coins, Bowser will give them 10 coins. He only leaves when a player has bought something.
Bowser will cause a huge sandstorm that destroys the bridges for three turns, leaving everyone stuck on the side they're on and blowing any characters on the bridges back to start. This also destroys the Orb Shops for three turns since they are located on the bridges. If Bowser took over an Orb Shop in the previous Bowser Time and nobody bought anything, his shop will still be there after the bridges are repaired.
Will steal a Star from the player in first place, then give it to Koopa Kid. Anyone who passed by Koopa Kid while on a Chain Chomp earned that star.
Will crush one of the windmills (always one that has been bought already). After this, a new windmill was built with no coins, thus no owner.
Will make Koopa Kid steal a random amount of coins from a random windmill. Sometimes, a Koopa Shepherdess would walk by, making Koopa Kid disguise himself as a bush. It is unknown if this effects the cost or not. There is also a small chance that Koopa Kid will not be able to steal any coins.
Will sink the island containing the star. Anyone who was on that island are sent back to the start and lose half of their coins. After this, the star would move to a new location on the board. After the first Bowser Time event, he will also raise up the island that he sank in the previous Bowser Time.
The fact that Bowser Time happens every 5 turns is the reason why the Last Five Turns Event was changed to the "Last Four Turns Event".