Phineas and Ferb: Summer Belongs To You!, on Disney XD & Disney Channel
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This hour-long special first aired in 2010, during season 2 of "Phineas and Ferb." Somehow I neglected to write a review of it, at the time, but I'm doing so in 2020, after re-watching it on Disney+. First I should say that it seems like it starts at the end of an opening song, and I can't remember if there actually was one that for some reason isn't included online, or if there never was an opening song. I suppose it's not important.

On the longest day of the year (which is technically the first day of summer, which is when I watched it in 2020, though back in 2010 it aired in August), Phineas and Ferb decide to build a plane to fly around the world so they can have a whole day of sun, making the longest day even longer. Since their parents had gone away for the day, Candace was left in charge of the boys, so she decides to go with them to make sure they don't get into trouble... but mainly she goes to see Jeremy, who's on vacation in Paris. Also joining them on the trip are Isabella, Buford, and Baljeet. Meanwhile, Dr. Doofenshmirtz is taking his daughter, Vanessa, on vacation to Tokyo, but she gets upset when she finds out he had kidnapped Major Monogram and brought him along, to frame him for doing something bad to a good guys convention.

Anyway... Phineas and friends' first stop is in Tokyo, where there's an anime-style song. Later there's a Bollywood-style song in Tibet. And Isabella does a song in Paris about being disappointed that Phineas isn't interested in romance with her. And um... well, there are some other songs, including the closing number which is also the episode's title, once they get back to Danville. And lots of other stuff happens throughout the special, which I mostly don't want to spoil. It was all definitely fun and funny, as usual, though I feel like I maybe didn't like it quite as much as I did when I first saw the special ten years ago. Back then I probably would have given it a slightly higher rating, but I still really enjoyed it. And I'm really glad I've finally re-watched it.