The story follows Phineas, Ferb, and his friends on Halloween night. In a true Phineas-and-Ferb fashion, Ferb is given, as they think, the coolest costume in history by being transformed by genetic engineering into a 200-pound green werewolf. Unfortunately, Ferb loses his mind shortly after Trick-or-Treating is over and begins to attack. Using Jessie's cleverness, Candace's strength, and Perry's venom, the gang tries to turn Ferb back to normal.
Its reviews have been almost universally positive, some even considering it one of the best fics ever written for the franchise.
A British Werewolf in Danville contains examples of:
- Action Dress Rip: Jessie tears the hem of her dress to run from the werewolf.
- Adults Are Useless: Major Monogram, literally the only adult who gets any screen time in this story, is the opposite of helpful.
- Becoming the Costume: Invoked by the brothers for "the best Halloween ever".
- Big Friendly Dog: Were Ferb, before he loses his mind and after he becomes sane again
- Big "NO!": Phineas lets one out when his brother falls off the edge of the multi-level parking lot.
- Deadpan Snarker: Baljeet gets this gem:Baljeet: "Um, yes. Why do I need to go with Buford?"
Phineas: "Because Buford needs you for his costume."
Baljeet: "Oh, goody, I cannot wait..."
- Death Glare: Baljeet receives one from Buford after questioning why he must look for costume supplies with him.
- Improbable Aiming Skills: Jessie's got 'em. It saves all the character's lives.
- Mood Whiplash: Things go from perfectly happy to entirely terrifying for the characters quite abruptly in Chapter 4.
- Noodle Incident: Okay, is there ever going to be a Halloween where I can trick or treat and not have to run for my life half the time? After the canon episode "That's the Spirit", kinda makes sense.
- The Only One Allowed to Defeat You: When Candace protected Phineas from Ferb as a Werewolf.Candace: "If anybodys gonna hurt this kid, its me!"
- Original Character: Jessie, Ferb's twin sister.
- Painful Transformation: Turning into a Werewolf doesn't seem to hurt, but turning into a deadly, bloodthirsty one does.
- She Cleans Up Nicely: Jessie's change into her Repunzel costume is described like this.
- Shout-Out: Several:
- The Mind Is a Plaything of the Body: Doesn't happen immediately, but eventually Ferb's Savage Wolves werewolf 'costume' makes him into one.
- Twin Telepathy: Ferb and Jessie. Justified by the fact that they have alien blood in their family.
- What Could Possibly Go Wrong?: It's the title of Chapter 2.