The X-Ray Glasses are the glasses Phineas and Ferb made after being ripped off by a fair of commercial brand X-Ray goggles. These glasses can see through any solid object, but apparently not all, or give you the power to see certain things. For example, when Phineas is wearing them in a store and is looking through cereal boxes to find a good prize, he could see the cereal and prizes in each box, instead of seeing the wall behind, or even outside. They begin to test their performance skills by going around town and using the glasses to help people, and themselves.
Isabella looking at Phineas and Ferb's skeletons with Phineas on the left and Ferb on the right, who then take off their heads and put on each other's. Isabella looks startled and takes off the glasses, to see Ferb on the left and Phineas on the right.
Helping workmen find a giant dinosaur skeleton underground.
Looking inside Buford and seeing all the stuff in his stomach (including a 1st place ribbon,a bird,a can of beans and a goldfish which looked a lot like Goldie.). Note: Obviously, this is impossible, seeing as his stomach was a big hole, Phineas could see everything inside of him, and he had no internal organs.
Seeing the men (inside a donkey costume) and the donkey (inside a clown costume) at a circus.
Finding a young child inside a fun bounce filled with plastic balls in someone's backyard. Ferb then used a grabber-arm to pull him out by his shirt.
Looking inside numerous houses:
Exterior - Normal looking ---- Interior - A woman hanging from a trapeze bar and a man lifting 2000 pounds.
Exterior - Gingerbread house style ---- Interior - A witch stirring a cauldron with a cat staring right at Phineas
Exterior - Soccer ball shape, icey-white, dome-shaped ---- Interior - Martians similar to those from Mars staring up at a tractor beam holding a cow in place above their heads ---- Note: This is the only house Phineas's reaction was shown, and he was clearly shocked/confused.
Looking inside certain cereal boxes in a store, searching for the perfect prize, a giant metal dinosaur toy.
Later in the episode, when the rabbit agent, Dennis, uses the glasses to look underground and find the secret entrance to Perry's lair under the ground.