(Scene opens on a shot of the Flynn-Fletcher house.) Gretchen: (offscreen) So we all need to be... (Cut to the backyard where Gretchen is making a presentation to Phineas, Baljeet, Ferb, and Buford with a diagram on an easel and a pointer.) Gretchen (cont'd): ...prepared. You'll want to find a safe place and establish a defensive perimeter. Baljeet: Like in the basement? Gretchen: No! You never go in the basement! Candace: What is going on here? Gretchen: It's just our bi-monthly Zombie Apocalypse preparedness lecture. Phineas: Yeah! You're welcome to join us. Ya might learn something. Candace: Puh-leez, Phineas. There's nothing about zombies that I don't know. Ferb: Did you know there's one standing behind you? Candace: AAH!! ...Very funny. Phineas: Ha! Good one, bro. Isabella: Phineas, P