Mom's Birthday, Journey to the Center of Candace

Candace plans a special birthday for Mom, and even a song, but Phineas and Ferb are always getting in her way of what she planned, unintentionally topping everything. Meanwhile, Doofenshmirtz creates a shrinking machine that will make whatever he hates implode.
Phineas and Ferb build a shrinking submarine so they can go inside Isabella's dog and retrieve a sash the pet ate, but they accidentally end up in Candace's stomach instead. Meanwhile, Perry must stop Doofenshmirtz from destroying people who can't make up their mind.