When Carl intercepts blue prints for Phineas and Ferb's Anti-Gravity Fun Launcher, he mistakenly thinks that they are assisting Dr. Doofenshmirtz with an evil plan so Major Monogram sends him incognito to uncover what the boys are doing.
When Mabel befriends a cute Merman trapped in the deep end of the public pool, she's determined to return him to his family in the ocean, even though that means her whirlwind romance will come to an end.
Feeling unappreciated by her family, Polly hatches a plan to make them pay attention to her. Hop Pop signs the family up to join a traveling theater troupe, hoping to realize his dream of being an actor.
Hop Pop drops Sprig and Polly off at an obstacle-filled mountain trail designed to help them get along. Sasha and Grime must reconcile their differences to escape Newtopia's most skilled warrior, General Yunnan.
It's Halloween night and the kids encounter a strange boy and his father who are convinced their house is haunted. Then, Candace is bitten by a bat after watching a popular vampire movie and worries that she is becoming a vampire.
Phineas and Ferb are inspired by an antique escape chamber to build a computer-controlled tower that allows them to explore the world of escapement. Craziness is going rampant in Danville, but no one has any idea what is going on.
Phineas and Ferb create their own language, Ferb Latin, which quickly catches on. Then, when all of the potatoes in Danville go missing, Phineas and Ferb decide to clone some using Buford's last potato chip, with unexpected consequences.
When a Burger Clown franchise opens next door, Cricket tries to prove to Bill that he can eat fast food for every meal with no ill effects. Then, Tilly and Cricket debate whether the lives of people in Big City are intertwined.
In three separate mysterious tales, Stan is cursed by a witch, Waddles accidentally eats a bowl of brain-enhancing jelly and builds a machine that allows him to speak for the first time and Mabel faces her fear of Claymotion.
Anne wants to keep a caterpillar as a pet, but she'll have to keep it a secret from Hop Pop; After one of the Plantars mysteriously runs out the charge on Anne's phone, the family embarks on a mission to try and recharge it.