Well, it turns out that the PnF crossover with Marvel superheroes is actually happening.
It turns out that there will be an episode of Phineas and Ferb called "Phineas and Ferb: Mission Marvel.
Here is the plot to the episode:
Spider-Man, Thor, Iron Man and Hulk arrive in town after their powers are accidentally removed by the evil Dr. Doofenshmirtz. Phineas and Ferb come to the rescue, and they work together to defeat some meddling Marvel villains, including Red Skull, Whiplash and Venom.
Here is a link to the article below:
So what do you guys think?