This is another of my favorite songs from Phineas and Ferb. It's a completely random song in the middle of their summer special. They are flying around the world, they land in Tokyo, and they all turn into anime characters and start doing a Caramelldansen parody. I love Candice's line at the end, it just sums up how completely random it was. "I have no idea what just happened."
As a bonus, I'm including one more from the same episode. After they leave Japan, they end up crashing in the Himalayas, quite coincidentally right near Baljeet's uncle's Rubber band factory. Musical hilarity ensues.