This is an episode of Phineas and Ferb where first Coop, from Kid VS Kat has been on their rides and he wants to meet them face to face. Meanwhile, Phineas and Ferb have nothing to do that day. Later Perry swipes his hat on and goes to his lair and finds out he has an alien mutant (Kat) in Phineas and Ferb's backyard becuase Coop gets there. Then Coop talks to Phineas and Ferb about how Kat is an alien from another planet and how he trys to get it in trouble. Candace hears Coop say that and asks Phineas and Ferb if she can talk to Coop. At Doofenshmirtz Evil Inc, Doof also has nothing to do that day so he uses his old Retireinator (the one for when he stops working). So Doof then remembers that Perry didn't return Norm yet so he goes out to find Norm. When Perry gets to the backyard with his dumb platypus look, really quick he gives an evil glare at Kat. Kat does the same. When Coop and Candace finish their conversation about busting the boys and Kat, they decide to go to the Fireside lodge becuase Candace had a Fireside meeting to go to. Then when Coop, Phineas, Ferb and Candace leave, the battle began. Perry swiped on his hat and Kat swiped out his claws. In the end of the episode it doen't show Phineas, Ferb, Candace or Coop again. In the end credits, it shows Doof going into a toy store (at night) still trying to find Norm. Then he sees Norm with the toy store clothes on and for the FIRST TIME, Doof runs over to Norm and hugs him and says "I will never leave you again, Norm!"
Carl (speaking cameo)
Irving (in the toy store when Doof hugs Norm saying, what a baby)
Perry the Platypus Flynn (Agent P)
When Doofenshmirtz goes in the store Norm's costume has the Har D Har Toys logo on it (Toy to the World)
When Candace leaves to go to the meeting she is wearing her Fireside girl clothes (Fireside Girl Jamboree)
There will be a Kid VS Kat version called Kat's Showdown.
Doof's Retireinator is in the episode, The Bully Code
Phineas and Ferb and Kid VS Kat are both owned by Disney.