Late at night on the balcony of Doofenshmirtz Evil Incorparated layed the evil scientist and his robot, Norm, looking at the night sky. "I don't know Norm," Doof said to his robot. "What type of scheme we should do tomorrow?" He asked. Suddenly, a bat flew up to him and bit him on the right side of his neck. "What was that?" Doof asked in alarm. "Sir, you have blood stains runining down from your neck." Norm said pointing his robotic arms towards where that bat bit him.
"What?" Doof said as Norm transformed himself into a mirror. "Oh-no!" Doof screamed waking up his goth daughter, Vanessa. "Dad, why are you screaming?" Vanessa asked opening her bedroom door. "I'm trying to sleep." She added. "Sorry, honey. I just have these blood stains down my neck." Doof apologized as he heard his daughter say "Whatever" as she went to bed.
"Norm, let's go to bed." Doof said as Norm converted himself into his robot version. "We'll figure this out tomorrow." Doof said tucking himself into bed and going to sleep with teeth marks on the right side of his neck.
The next day...
"Sir, I have done some research and based on those marks and blood stains on your neck last night, it looks like you've been bitten by a vampire!" Norm said as Doof walked into the kitchen to have breakfast. "Seriously Norm, It's not even halloween!" Doof said as he felt the bite marks with his fingers. "Maybe, if I can use my vampiric powers, I can trap Perry the Platypus and I can suck his blood!" Doof said.
"We can think of a scheme so evil that Major Monobrow will send Perry to us, you'll put him to sleep with this weird watch I found and then I will bite his neck and then Perry the Platypus will become, Perry the Vampire!" Doof said as he thought about his nemesis becoming a blood-sucker.
At Perry's house...
"So, Ferb. What do you wanna do today?" Phineas asked his step-brother. "I don't know. Maybe we can ask Candace to turn us into vampires! Cuz she is still one. Maybe, Perry can jon us!" Ferb suggested. "Whattaya say Perry? Perry?" Ferb asked as he noticed that the semi-aquatic platypus somehow disappeared.
In Perry/Agent P.'s layer...
"Good morning Agent P." Major Monogram said to his platypus agent. "It seems like your nemesis, Dr. Doofenshmirtz, has created some sort of inator that can turn animals evil. Your job is to get out and stop him before he turns O.W.C.A into his own evil headquarters." Major Monogram said as Perry saluted and he flew off to DEI in his hoverjet.
*Doofenshmirtz Evil Incorparated*
"Hello, Perry the Platypus!" Norm said shaking the watch infront of Perry's bill. "Grrrggrrgg." Perry chattered as his eyes followed the watch and he fall to his feet. "Now, I can taste platypus blood!" Doof said appearing in a black cloak. He bit Perry on the neck and suddenly Perry's skin turned a pale-teal as the poison was in his blood.
Moments later, Perry woke from his slumber and found he was now in a bat cage. What happened? Perry thought "Welcome Perry the Platypus to your new life!" Doof said walking close to the cage. Perry tilted his head in confusion. "As a vampire! HAHAHAHA!" Doof said revealing his own fangs and the-now healed marks on the right side of his neck.