Linda is about to leave while Phineas and Ferb are sick in bed. Before leaving, she asks if they'll be fine by themselves, to which they respond positively. After Linda leaves shortly, Candace comes in and asks if they are sick. Phineas optimistically tells Candace not to worry, sneezes, and then replies that nothing can stop them. Candace happily thinks about Jeremy related activities out loud, and leaves.
Candace does not seem to realize that her brothers have made a system with their friends so that they can talk via microphones and a television screen. Isabella greets them with her catchphrase, and then sneezes. Both Baljeet and Buford come on, and they all cough and sneeze except for Ferb and Buford. Buford says he is not actually sick, just lazy. Phineas wonders where Perry is, and everyone looks in their beds.
Perry walks past Phineas and Ferb's room. He stands up and puts on a surgical mask before heading over to his lair, where Major Monogram makes a comment about the surgical mask, and Carl adds his thought. Perry takes off the mask and Major Monogram starts the briefing: Dr. Doofenshmirtz has been making purchases at Brain Bath & Beyond. Being assigned to find out what Doofenshmirtz is doing, Perry leaves in his hovercraft.
Perry arrives at Doofenshmirtz Evil Incorporated. He walks to a chair with an empty table, where he hears Doofenshmirtz's voice, but he sees no one. Suddenly, Doofenshmirtz swings from a rope and puts a helmet on Perry's head. After the helmet locks into Perry's head, Doofenshmirtz tells Perry he can control his actions with his new invention: the "De-Volitionator" which was, according to him, "not to be confused with the "De-Evolutionator" from "a few schemes ago."" Doofenshmirtz makes Perry get off of the chair and walk towards him then explains that volition is the power to choose what he is going to do.
Meanwhile, back at Phineas and Ferb's room, Phineas and the kids are about to play a video game. The first round is Buford versus Isabella. Buford knocks Isabella down. She stands up and gets her sash. She ties him up and pulls, sending Buford spinning away.
Meanwhile Charlene is driving Vanessa to a party at the Danville Scrap Yard. She tells Vanessa that since she will be busy doing her nails, she has called in Heinz to pick Vanessa from the party. This doesn't seem to suit Vanessa pretty well: in a flashback, Dr. Doofenshmirtz (wearing a diaper and a baby hat) is seen picking up Vanessa from school in a tricycle with a wagon tied to the back. The other students laugh as Vanessa gets in the wagon. Back in real life, they arrive and Vanessa greets Johnny before Charlene leaves.
Back in Phineas and Ferb's room, they start their next round: Baljeet and Ferb. Baljeet complains that Ferb is the Gaming World Champion and he would easily lose. Ferb runs toward Baljeet, and Baljeet kicks him. He punches Ferb, who loses. Baljeet asks if he intentionally let him win because he didn't want to hurt his feelings. Showing a pendulum duck hitting the forward button, Ferb replies, "Oh, I'd never do that," while reading a book.
At Danville Scrap Yard, Vanessa and Johnny finally catch up to the party. There are cameras set up to record everything; including themselves, the crowd, the DJ, and the toilets (much to the dismay of one of the boys who's using them). In Phineas and Ferb's room, Phineas wonders who he will fight, either Isabella or Baljeet. The next round is Phineas verses Phineas. Because he is playing both of himself, they kick each other, and fall to the floor. He exclaims that he is "kicking his own butt."
As Doofenshmirtz is walking Perry to Bazar's Car Parts, he makes Perry skip around and slap himself so many times, much to Doofenshmirtz's amusement. Afterwards, Doofenshmirtz makes him pick up a piece of gum from the floor to put it in his mouth (much to Perry's distraught). Before it gets in his mouth, Doofenshmirtz stops Perry, then decides it was so funny he makes Perry put the gum down to do it again. From the park, Doofenshmirtz calls Vanessa at the party, where he explains of the fun, he's having fun making Perry do what he tells. He also tells her that he will pick her up along with her Visigoth friends, though Vanessa corrects her father by saying that the name is Goth, not Visigoth; and that her friends are Punk, not Goth. After Vanessa hangs up, Doofenshmirtz talks to someone dressed as a Visigoth barbarian. The barbarian leaves, disappointed that he doesn't get to go to the party. Doofenshmirtz them returns to making Perry slap himself.
Later on, Perry is pushing Doofenshmirtz inside a shopping cart, arriving to the Danville Scrap Yard. One of the kids compliments on this, to which Doofenshmirtz responds as 'platypus power'. However, Doofenshmirtz realizes that the remote's battery is low, so he tried to plug it into the battery running the party's cameras to recharge it. However, it does not work, and the resulting electricity is sent through the power lines to the Flynn-Fletcher house. On Phineas and Ferb's video game, instead of seeing Phineas and Buford fight the signal from one of the cameras shows Perry and Dr. Doofenshmirtz on screen. Phineas realizes that he can control Perry's left arm with his game controller; Isabella can control his left leg; Buford can control his right arm; Ferb can control his right leg; and Baljeet can control his forward and backward movement. At first, they start making Perry slap himself, which made Doofenshmirtz realize that he can no longer control Perry anymore.
Thinking that Doofenshmirtz is a game villain boss, the kids control Perry to fight him in the "Perry level." After having Perry to jump down on Doofenshmirtz chest many times, Buford has made Perry catch a fly and eat it thinking that it is a power up. This left Perry somewhat sick, even the horrified Doofenshmirtz finds this to be more disgusting than the sidewalk gum. Seeing that Perry has literally gone out of control, Doofenshmirtz gets scared and runs away to climb one of the scrap piles. Perry basically lets his involuntary movements do the fighting for him. Doofenshmirtz manages to grab an umbrella, Perry seizes it, and he finally kicks Doofenshmirtz off causing him to roll down the pile. Phineas claims the right to throw Perry's hat in the air, removing the helmet and it lands on the camera. They lose the signal, and everyone groans. Despite this, Perry is now relieved that he is finally free from the helmet's control.
As Doofenshmirtz is rolling down the pile, he accidently gets his hands covered in glue. He lands on the DJ controls for the party, where he accidently puts his hands on the records, and the music stops, and everyone is silent. Johnny asks Vanessa if he is her dad, but she lies to no avail. As someone comments on what's going on, the crowd starts to boo Doofenshmirtz for interrupting the music (despite that he had no intentions of doing so). Doofenshmirtz is unable to get the records off his hands (since they're stuck) and starts to get extremely nervous. Perry attempts to leave, but upon seeing a scared Doofenshmirtz facing the wrath of the crowd, he starts to feel extremely bad for making Doofenshmirtz look silly, knowing that Vanessa will hate him for this. Unwilling to let the situation get any worse, Perry gets Doofenshmirtz's attention and puts the mind control helmet on him, making Doofenshmirtz scratch the records. While doing so, Doofenshmirtz subconsciously sings a rap about a platypus controlling him. The crowd is impressed by this and starts to follow along to the beat, believing that the platypus is a metaphor for the things that control them. Doofenshmirtz attempts to tell the crowd that it is not a metaphor, but when he realizes that Perry has left and seeing Perry giving him a thumbs up, a cheered Doofenshmirtz continues playing the beat on his own. The whole crowd then praises Doofenshmirtz for his fantastic beat; even Johnny find this to be extremely cool. Proud by her father's efforts for making himself look cool to everyone, Vanessa happily walks over to him and kisses him on the cheek as thanks. Afterwards, Vanessa joins in dancing with the others as Doofenshmirtz happily continues scratching the records.
Phineas and Ferb are still in their room and Phineas replies that all their fevers are broken while Buford got sick from lying in bed all day. They see Perry come in. Phineas comments about giving him a walk, but Perry chatters wearily on this, having grown tired being controlled by Doofenshmirtz.