Don't Even Blink

Candace tries to figure out how 's crazy creations disappear every time before their mom sees it. Doofenshmirtz creates an Invisible Ray to make the Fireside Girls invisible when they come knocking to sell him cookies.

Episode Summary
The day begins with Candace scheming to bust Phineas and Ferb, but Stacy says that she is focusing to much in the boys, and that if she took her mom to the place where the invention goes, she could bring her mom there therefore busting them more easily. They ask Phineas and Ferb to build a "big and obvious" invention, so that they can watch it.

Agent P then appears behind Candace and Stacy while they're watching the invention, and sneaks over to a lair entrance which then pops out of the ground in the form of a box-elevator with many Casino style lights, decorations and sounds, but luckily the girls were watching the ride so intently that they do not see or hear the box, and Perry is able to get to his lair unnoticed. Major Monogram then tells Perry that he made the entrance that way so as to help get him in the mood for his upcoming trip to Las Vegas. He then says that Dr. Doofenshmirtz is making an invisibility ray, etc.

Meanwhile Phineas and Ferb invite Isabella, Buford and Baljeet to help watch the ride with them. Perry then arrives at Doofenshmirtz Evil Incorporated, enters the building, and gets trapped in an invisible cage which contained an invisible tin cup to occupy Perry while trapped in it.

Doofenshmirtz then shows him the Invisinator, a ray that could cause objects to become invisible, which he plans to use on the Fireside Girls when they come to sell him cookies. He tells Perry that he was annoyed that when he left his shades up, they could see that he was home, so he couldn't just ignore them and pretend he wasn't home, and they would make big pleading eyes that make him feel guilty, so, rather than shooting himself with the ray so they don't see him, he decides to shoot the girls with it so that he won't have to look at them.

Perry begins to file at the bars of his cage with a invisible file, so Doofenshmirtz is driven to release his invisible tiger, but instead of attacking Perry, it attacks Doofenshmirtz. He manages to drive the tiger back through the trapdoor, and closes the door. But Perry, it seemed, had already escaped. Perry, swinging on a rope, kicks Doofenshmirtz. Doofenshmirtz rolls through the invisibility ray, leaving him completely invisible. Doofenshmirtz thinks Perry will be unable to find him, and doesn't refrain from telling Perry so. This, however, allows Perry to locate him, and Perry gives him a series of kicks and punches, making him to roll back through the invisibility ray, causing him to become visible again. Doofenshmirtz remarks that he didn't know that it could do so. Perry then throws a chair through the ray, at Doofenshmirtz.

Meanwhile, Candace realizes that the rides usually only disappear after the kids are done playing with it. She then tells the kids to go play on it. They do, and have fun doing so.

At Doofenshmirtz Evil Incorporated, the fight continues. Doofenshmirtz punches Perry, making him go flying part-way into the ray of invisibility. Perry's head becomes invisible. Perry then gives Doofenshmirtz a series of punches, causing Doofenshmirtz to fall over backwards. He gets up and runs at Perry. Perry grabs his arms and flips him over onto his back, causing his legs to go into the ray. Perry jumps at him, causing them both to go through the ray again, making the parts of them that was invisible to become visible. Perry starts running away from Doofenshmirtz. Doofenshmirtz jumps over Perry, stopping Perry. Doofenshmirtz picks Perry up, and throws him through the ray. Perry aims the ray at Doofenshmirtz's top, causing him to be completely visible again. Perry then proceeds to make himself visible again, sticking his head in the ray.

Back at Phineas and Ferb's house, the kids get off the ride. At that moment, Perry jumps off the ray, causing it to aim down at the ride. Mrs. Flynn gets home, and everybody looks around toward the driveway. The ride becomes invisible, just as they turn back towards the ride. Candace asks Phineas what he did, and he answers he doesn't think he did anything. Candace realizes it must be because her mom comes home that the inventions disappear. She asks her mom to back down the driveway. As soon as the car is moved, the ride becomes visible again. Candace asks her mom to come back up the driveway, and the ride disappears again. Candace thinks there must be some sort of sensor in the driveway.

She starts moving back and forth. The ride disappearing and reappearing in correspondence to her movements. Her mom decides to park in front of the house instead. Candace thinks she'll be able to see it from the front, but as soon as her mom looks, it disappears. Phineas discovers that the ride is just invisible. Candace goes to feel it. She then decides to use paint to make it's shape visible. She goes to get the paint.

Meanwhile, Perry and Doofenshmirtz are still dueling. He tells Perry that with only the push of a button, he can turn the invisibility ray into a disintegrator. He does so, and the ray shoots at the ride in the backyard, duly destroying all evidence of its existence. Perry then proceeds to aim it at the control panel of the ray, instantly disintegrating it.

Back at the house, Candace is running towards the ride, planning to throw the paint all over it. But, since it isn't there, the paint just lands on the ground. Linda announces that all the kids and Candace, once she cleans up the paint, are welcome to come in for some cookies. Ferb tells Candace that the Quantum Theory states that the mere observation of an experiment changes its outcome, and the day ends.

Songs

 * Watching and Waiting
 * Quirky Worky Song

The "Too Young" Line
none

Ferb's Line
(To Candace) Well, we were all watching it, and Quantum Theory states that the mere observation of an experiment changes its outcome.

Whatcha doin'?
Said by Isabella when she walks into the yard.

Perry's entrance to his lair
A box comes out of the ground looking like a Casino entrance

Background Information

 * Premiered on Disney XD on April 4, and on Disney Channel US on May 29.
 * The beginning of the song "Watching and Waiting" looks like the scene from Unfair Science Fair Redux (Another Story) with the man, whose job is to watch over what is happening on Mars through the Mars Rovers, who was just sitting while waiting for something to show up.

Continuity

 * This is the third time Perry's theme song has played.

Allusions

 * Carly Simon: "Watching and Waiting" has a similar music style and opening to "You're So Vain", one of Simon's Biggest Hits.
 * Doctor Who: The name "Don't Even Blink" may be a reference to the Doctor Who episode "Blink" in which The Doctor says "Don't even blink."

Cast

 * Vincent Martella as Phineas Flynn
 * Ashley Tisdale as Candace Flynn
 * Thomas Sangster as Ferb Fletcher
 * Kelly Hu as Stacy Hirano
 * Dan Povenmire as Dr. Doofenshmirtz
 * Jeff "Swampy" Marsh as Major Monogram
 * Dee Bradley Baker as Perry the Platypus
 * Caroline Rhea as Linda Flynn
 * Maulik Pancholy as Baljeet Patel
 * Alyson Stoner as Isabella Garcia-Shapiro