Phineas, Isabella, Baljeet, Buford and Thaddeus are hit by cosmic rays in a rocket test, and gain superpowers. Phineas gains unlimited elasticity and flexibility. Isabella has the ability to bend light energy to turn invisible, and project forcefields. Baljeet gains the power to ignite his body in flames, shoot fire and fly (to which he has no control.) Buford's body turns to a living stone, and increased strength.
The four kids unite to form the crime fighting force known as the Phintastic Four. But Thaddeus, whose body turns to steel and gains power over electricity, schemes against the heroes and makes plans to rule the world.