Phineas, Ferb & Sonic: Halloween is the Halloween special of the Xros-Over Series, with Knuckles being held hostage on Angel Island's Haunted Hill Zone. The chronological prequel is Phineas, Ferb & Sonic: Adventure and the chronological sequel is Phineas, Ferb & Sonic: Christmas Spectacular.
Summary[]
Chapter 1: Halloween (Part 1)[]
A knock was at a door with a sign that says “Halloween in Progress!” Sonic in his Way Past Cool Halloween costume heads to the door to see his friends Phineas, Ferb and Isabella.
“Hey guys, Great costumes!” Sonic tells his friends to see Phineas is dressed like him, Isabella is dressed like Amy and Ferb is dressed like Knuckles.
“Ferb, why are you Knuckles?” Sonic asks and Ferb replies “This is the only costume that was left at the store!”
Sonic takes a look at his list to see Knuckles is the only person he invited not at his party, and then Sonic says “Hey where's Perry?”
Back on Phineas and Ferb's world Perry walks over to a candy basket and hops in. He lands in his lair but a few SugarPopers fell in to.
“Good Evening, Agent P. Dr. Doofenshmirtz is up to some tricks...” a rim-shot is heard, “Carl!”
“Sorry Sir.”
“Well go stop him!”
Perry salutes and hops into a candy cart, and drives to Dr. Doofenshmirtz's base.
(♪Doofenshmirtz's Evil Incorporated During Halloween♪)
“Oh no! Have to keep Warp Ring sealed!” Doofenshmirtz tells himself, when a knocking sound is heard.
“Take a candy.” was Doofenshmirtz's reply, but Perry chatters. “Oh, Perry the Platypus!”
Doofenshmirtz walks over and opens the door. “Oh Perry, look no scheme today! I'm trying to clog the Warp Ring! Dr. Eggman caused nothing but misery, back at collage!
“Good Morning Doc!” Doofenshmirtz tells his roommate, to see Eggman is gone then he looks outside to see loads of Egg Fighters storming the school.
“Oh great! My Egg Fighters are on a sugar rush!”
“Hey set the Egg Fighters to “Attack Mode”, and they nearly broke the entire building! So, I'm blocking the Warp Ring so he won't attack this year! Hey Perry can you help me!” Doofenshmirtz asks. Perry just grabs some boards and quickly puts them over the Warp Ring.
“Oh thanks Perry. Hey do you have any SugarPopers? I love them!” Doofenshmirtz tells Perry, he rummages through his hat and pulls some out.
“Oh thanks Perry. So I'll show my Duplic-8-inator 2.0.! It'll duplicate anything 8 times and the 2.0. means it'll double by 2! So it'll duplicate anything 16 times!” Doofenshmirtz tells Perry, he walks over and puts the SugarPopers in front of the inator and gets more.
“Let's eat!”
Chapter 2: Enter the Haunted Hill Zone[]
“Okay guys, all festivities are postponed until we get Knuckles!” Sonic tells the group, but he sees Phineas, Ferb and Isabella aren't there.
“Hey guys let's move!” Phineas tells his friends, Sonic walks outside to see MetalGreymon and Shoutmon ×5.
Sonic and his friends hop on and Phineas yells “Next stop: Angel Island!”
Master Emerald Altar
“This makes no logical sense! We searched this island top to bottom, Knuckles isn't in any of the Zones here!” Phineas yells as he takes a map of Angel Island out, Sonic grabs the map and sees an orange area on the map marked “?”.
“Um, Phineas you due know this Zone is the Haunted Hill-”
Before Sonic finishes talking Ferb covers his mouth, and Phineas says “Huh, well, we haven't looked in this unmarked Zone, let's go.”
Phineas and the group starts walking with Sonic turning over to Ferb, Sonic asks him. “What was that for?”
Ferb replies “That Zone haunts Phineas to this day, so when we get there...”
Ferb stops talking when he sees the outskirts of the Zone. He walks over to his stepbrother and turns Phineas around and tells him “We need you and Sonic in reserve in-case we need back-up.”
“Oh, okay.”
Ferb takes the others deep in the heart of the Zone.
(♪Doofenshmirtz's Evil Incorporated During Halloween♪)
“So, Perry, how are the boys, what are they up to?” Dr. Doofenshmirtz asks Perry, so he pulls out his translator collar and replies “Oh, fine, they're on Mobius, Sonic's having a party.”
Then a giant claw pulls the Duplic-8-inator 2.0. right into the Warp Ring, with Dr. Doofenshmirtz.
“Save me Perry the Platypus!”
(♪Robotropolis♪)
“Eggman, why did you kidnap me?”
“It's Halloween! Now I'm going to invade Angel Island with the new Inator you built!”
Perry hopes in hits the self-destruct button on the Duplic-8-inator 2.0., but not before Eggman shots loads beams...
With Ferb
The team walks into a room to see a single ghost with Ferb like “okay, we can handle this, on and there’s Knuckles” but the beam makes 200, copies of the ghost and Ferb is like “oh crud!”