Phineas and Ferb: Mission Marvel, on Disney Channel & Disney XD
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This is an hour-long Phineas and Ferb special that originally aired in August 2013, and then was released on DVD in October of that year. But I didn't see it until 2022, on Disney+. I thought it was incredibly funny and the show really meshed perfectly with the Marvel characters.

Phineas and Ferb and their friends are surfing on an asteroid belt. Perry the platypus destroys Dr. Doofenshmirtz's latest inator, which was supposed to drain powers. (He wanted to use it on his brother, to drain all his mayoral powers, but didn't get that chance.) After it's destroyed, the power drain-inator sends out a beam that bounces off Phineas and Ferb's space station satellite, and gets redirected to New York City, where Thor, Iron Man, Hulk, and Spider-Man are battling Red Skull, Venom, MODOK, and Whiplash. The villains are defeated but get away, and then the heroes are hit by the inator beam, which drains them of their powers. They go to SHIELD's helicarrier, and learn about the beam having originated in Danville and bounced off the space station, so the heroes go to see Phineas and Ferb. Meanwhile, Doofenshmirtz posts online about having drained the heroes' powers, and that post is seen by MODOK, so the villains all go to see him, to get his help. SHIELD director Nick Fury contacts Perry the Platypus through Major Monogram, and Perry dons a superhero costume to fight the villains. Phineas and Ferb also use a robotic superhero suit to help the heroes. And they create a machine to temporarily give the heroes simulated powers, but the powers get mixed up because of Candace trying to help, which makes Phineas angry at her. Later, Candace tries to help again, and causes another problem. So she's upset about that, while Isabella is upset about being excluded, herself. Then Isabella gets an idea that... I'm not going to tell you about, because I've already said quite enough about the plot. But I will say it's pretty cool that most of the Marvel characters are voiced by the same actors that play them in Ultimate Spider-Man and Avengers Assemble. Plus Stan Lee plays a role. And... there's just so much good stuff in the special, pop culture references and whatnot. I don't know what else to tell you.