Dr. Doofenshmirtz and Major Monogram have their hearts set on revealing the top 10 musical numbers from Seasons 2 and 3, but soon find out that celebrity host Kelly Osbourne has been brought in to fill the role. Unwilling to submit to playing second fiddle, Doofenshmirtz makes it his mission to thwart Kelly until Perry the Platypus sets out to stop his nemesis from ruining the entire show. Maia Mitchell ("Teen Beach Movie") also guest stars.

Phineas and Ferb build a wall for climbing. Candace is recording a Fireside Girls book with Irving and loses her voice. Meanwhile, Dr. Doofenshmirtz creates the Just-Desserts-inator.