In the title sequence used in the first season of Phineas and Ferb, we see scenes that turn out to be from episodes in a later season.
Considering that according to the Phineas and Ferb Wiki,
At San Diego Comic-Con 2013, Dan Povenmire revealed that he wrote 104 because he only expected the show to last 52 episodes, like most Disney Channel shows lasted at the time, and there were two segments per episode, making it 104.
it's safe to say that the third and fourth seasons hadn't been planned at that time.
But still, we see Rover, the robotic dog, who first shows up in the third season "Canderemy". Does this mean that the episode had already been planned or even (partially) produced at the start of the first season? Or did they add it to the episode to account for the scene in the title sequence?
The same goes for the nanobots, which show up in the third season episode "Norm Unleashed".
In general,
Were any episodes created to account for scenes in the title sequence?
Or were all these episodes at the bare minimum planned at the time the title sequence was created, so that the creators only included scenes that they knew would be part of a later episode?
Or were they earlier episodes that had already been produced, that were pushed back to a later season for other reason?
"Mom, Phineas and Ferb are making a title sequence!"
