She had a very busy schedule, but was able to squeeze in 6 minutes to go shopping at the Googolplex Mall. While at the mall, she met Candace Flynn. After explaining to Candace how they are doppelgängers, Princess Baldegunde suggested that they spend the day together and freak people out. Candace said she would love to, but explained how she had to finish shopping and how her brothers were building some impossible thing in the backyard. Princess Baldegunde described how she never got to do anything herself, and since Candace said she had to everything herself, they agreed to trade lives.
Dressed as Candace, the princess went to the Flynn-Fletcher household and met with Phineas and Ferb in the backyard. They told her that they were building a giant jukebox. She was excited to join in the construction.
Isabella, Baljeet, and Buford came over to see what Phineas and Ferb were doing that day. Due to "Candace's" strange behavior, Buford left after she told them about building the jukebox. Phineas and Ferb noticed that she was really enjoying herself and had acquired an upper class Drusselsteinien speech pattern, but they decided to just go with it.
After the jukebox was built, and as they were filling it with different bands, she noticed Jeremy. She called Candace to ask her how to pronounce his name, calling him "cute blond boy with guitar." Candace angrily yelled at her to stay away from him, but the princess had already hung up. Soon Candace rushed into the backyard to tell the princess to stay away from Jeremy. However, after Candace saw the jukebox, she rushed inside to get mom. Meanwhile, Princess Baldegunde's royal attendants came into the backyard and took the princess to get ready for the award ceremony. As they were leaving, Dr. Doofenshmirtz's giant claw picked up the jukebox.
At the ceremony, she was beginning to give her speech, when Doofenshmirtz's claw dropped the jukebox on top of the opera house. Instead of giving her speech, she decided to use the jukebox and have Jeremy and his band, Jeremy and the Incidentals, perform a song. ("Make Play")
Candace is Princess Baldegunde's doppelgänger, or look-alike. They first met in the Danville Mall, and due to their identical appearance, decided to trade lives for a day. However, when Princess Baldegunde told Candace she thought Jeremy was cute and asked her how to pronounce his name, Candace decided she wanted her life back.
While disguised as Candace, she met Phineas in Ferb in their backyard and helped build their big idea of the day, which was building a giant jukebox. They noticed "Candace's" unusual enthusiasm and upper class Drusselsteinien accent, but decided to just go with it. They were there when the real Candace came into the backyard and when the princess's royal attendants took the princess away to get ready for the ceremony. They appear to be the only ones, other than Candace, that know about the switch.
Princess Baldegunde went to Danville to give the Drusselsteinien Favorite Son Award to Roger Doofenshmirtz and to give a speech in his honor. When the giant jukebox landed on top of the opera house, she decided to have Jeremy and his band play a song instead of giving her speech.
Princess Baldegunde is identical in appearance to Candace and also has a similar voice, except for her upper class Drusselsteinian accent. Like Candace, she is also voiced by Ashley Tisdale.
She appears to find her life as a princess boring and idolizes the life of American teenage girls, such as Candace.
Her name might be a parody of the name Kunigunde, which was a popular name for Medieval princesses (especially in Germany).
The idea of Princess Baldegunde and Candace exchanging roles is similar to the one in the classic Mark Twain novel The Prince and the Pauper.