Although Brandy did not appear much in the first season, her origins were shown in the episode "The Substitute", where Milo Murphy and his friends accidentally created a sentient blob that attacked the students and two time-traveling agents named Vinnie Dakota and Balthazar Cavendish. In the end, the blob left the school and came into contact with a broken pistachio sapling on the lawn, causing it to be replenished to its former glory and resulting the birth of King Pistachion, who would breed his own army of Pistachions (including Brandy) to take over the world.
Brandy was known for helping out her father and their fellow Pistachions in taking over the world in the year 2175. She is easily recognized having black hair and wearing a purse with her phone inside.
Following the successful capture of the majority of the people (including Mr. Block, the head of the Time Bureau), Brandy was seen among cheering with her fellow Pistachions as King Pistachion declares the entire world to be under their control. As King Pistachion declares that he will take a picture as a memento for the occasion, he asks Brandy to hand over her phone for the event, to which she happily obliges.
As King Pistachion takes a picture of himself and his horde, he notices three humans (Milo Murphy, Balthazar Cavendish and Vinnie Dakota) on the background as they have avoided captivity. As such, King Pistachion orders Brandy and the others to get the trio, but the trio managed to get into their time machine to escape, prompting an annoyed King Pistachion to use his own time machine to stop them.
However, in the present, Milo gets his dog Diogee to pee on a rare pistachio plant, which happens to be the exact same plant that King Pistachion was born through. With the pistachio plant destroyed, King Pistachion and his horde ceased to exist, and it can be implied that Brandy herself is erased from existence along with her fellow Pistachions in the future.