The Phineas and Ferb's backyard fort is built when Phineas and Ferb competed with Thaddeus and Thor to see who could build the best backyard fort ("Thaddeus and Thor"). As expected, Phineas and Ferb's fort turned out to be much larger and cooler than Thaddeus and Thor's.
When the fort was first revealed to the public, it appeared to be small and basic. However Ferb then used a remote which caused the fort to rise to 10 stories high. Each floor was designed differently, and the fort included a "Terracotta Army" room, a "Wind tunnel" room and a Bowling alley. Phineas also stated that the top floor was modeled on an old classic.
- Main entrance (marble flooring)
- Pool (with slide)
- "Terracotta Army" room
- "Jet engine wind tunnel" room
- Bowling alley
- The bottom floor looked like a castle.
- When the fort went down, a patio was seen.
- The top floor was the "little kid" fort.
- A Chinese-styled building was attached to the fort.
- At the end of the episode, the fort still stood (top floor only) in the Flynn-Fletcher's backyard.
- It, however, didn't have a licorice dispenser.
- It is unknown what happened to the fort after the episode it's in, as it was not seen from then on.