The Beanstar is a small yellow star with a green outline. When it is awake, it is smiling. However, when it hears the wrong voice, it turns red and looks angry.
It is central to the plot of the game, as Cackletta wants to steal it. It can grant wishes, but it can only be awoken by someone with a pure voice. Since Princess Peach is the only one in the world with a voice so pure, Cackletta steals her voice and uses it to wake the Beanstar. However, the Beanstar shatters into four pieces. when Cackletta uses Peach's voice on it. Later, Prince Peasley explains that Cackletta stole Birdo's voice instead of Peach's, causing the Beanstar to shatter. Birdo was disguised as Peach by magic. The Bros. then need to collect the pieces of the Beanstar, which are scattered around the kingdom. The pieces are located in Gwarhar Lagoon, Harhall's Studio, Yoshi Theater, and Chucklehuck Woods. After the four pieces are reunited, Mario and Luigi are contacted by Bowletta, who tells them to take the Beanstar to Joke's End, where she will obtain it. Peasley gives them a Fake Beanstar so that they will not have to give Bowletta the actual Beanstar. However, this plan does not work, and the real Beanstar is taken. In order to rescue Peach and obtain the Beanstar, Luigi disguises himself as the princess. Luigi says that the Peach they have is the fake. The villains fall for it, and Peach is returned to Mario. Luigi is then discovered by Bowletta and Fawful, and he flees the Koopa Cruiser, the ship that they had used to carry the Beanstar, taking it with him.